[4.7] HTLM Builds but fails to run with sBase64 is Null Error

Launching HTML version appears to build, opens browser, downloads then starts ‘running’ and stops with above error.

HTLM Log

LogHTML5Launch:Display: Starting UE4 ... 

LogHTML5Launch:Display: Command line:    ../../../CubeMark/CubeMark.uproject   /Game/Maps/Menu     -Messaging     

LogTemp:Display: PreInit Start
LogInit:Display: Running engine for game: CubeMark
LogInit:Display: Project file not found: ../../../CubeMark/CubeMark.uproject
LogInit:Display: 	Attempting to find via project info helper.
LogUProjectInfo: Found projects:
LogConfig:Warning: Failed to saved backup for config[Engine]
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LogConfig:Warning: Failed to saved backup for config[Game]
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LogConfig:Warning: Failed to saved backup for config[Input]
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LogConfig:Warning: Failed to saved backup for config[Scalability]
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LogConfig:Warning: Failed to saved backup for config[GameUserSettings]
LogInit: Version: 4.7.0-2455222+++depot+UE4-Releases+4.7
LogInit: API Version: 2455222
LogInit: Compiled (32-bit): Feb 21 2015 23:34:01
LogInit: Compiled with Clang: 3.3 
LogInit: Build Configuration: Development
LogInit: Branch Name: ++depot+UE4-Releases+4.7
LogInit: Command line:    /Game/Maps/Menu     -Messaging     
LogInit: Base directory: 
LogInit: Rocket: 1
[2015.02.24-23.15.48:878][  0]LogTaskGraph: Started task graph with 2 named threads and 3 total threads.
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[2015.02.24-23.15.48:882][  0]LogOnline:Warning: No default platform service specified for OnlineSubsystem
[2015.02.24-23.15.48:885][  0]LogInit: Presizing for 0 objects not considered by GC, pre-allocating 0 bytes.
[2015.02.24-23.15.48:928][  0]LogInit: Object subsystem initialized
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[2015.02.24-23.15.48:949][  0]LogConsoleResponse:Warning: Skipping Unknown console variable: 'UIScaleRule = ShortestSide'
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[2015.02.24-23.15.48:952][  0]LogConsoleResponse:Warning:   Found in ini file '../../../CubeMark/Saved/Config/HTML5/Engine.ini', in section '[/Script/Engine.RendererSettings]'
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[2015.02.24-23.15.48:955][  0]LogConsoleResponse:Warning: Skipping Unknown console variable: 'UIScaleCurve = (EditorCurveData=(Keys=),ExternalCurve=None)'
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[2015.02.24-23.15.48:958][  0]LogConsoleResponse:Warning:   Found in ini file '../../../CubeMark/Saved/Config/HTML5/Engine.ini', in section '[/Script/Engine.RendererSettings]'
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[2015.02.24-23.15.48:964][  0]LogConsoleManager:Warning: Console variable 'r.MSAA.CompositingSampleCount' wasn't set (Priority ProjectSetting < Scalability)
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[2015.02.24-23.15.49:036][  0]LogConfig:Warning: Failed to saved backup for config[DeviceProfiles]
[2015.02.24-23.15.49:045][  0]LogInit: Setting Device Profile CVar: [[r.RefractionQuality:0]]
[2015.02.24-23.15.49:048][  0]LogInit: Computer: Browser
[2015.02.24-23.15.49:051][  0]LogInit: User: GenericUser
[2015.02.24-23.15.49:053][  0]LogInit: Current Culture: en-US
[2015.02.24-23.15.49:055][  0]LogInit: High frequency timer resolution =1.000000 MHz
[2015.02.24-23.15.49:057][  0]LogInit: Memory total: Physical=1.0GB (1GB approx) 
[2015.02.24-23.15.49:066][  0]LogRHI: Initializing OpenGL RHI
[2015.02.24-23.15.49:069][  0]LogRHI:   GL_VENDOR: Mozilla
[2015.02.24-23.15.49:071][  0]LogRHI:   GL_RENDERER: Mozilla
[2015.02.24-23.15.49:073][  0]LogRHI:   GL_VERSION: WebGL 1.0
[2015.02.24-23.15.49:076][  0]LogRHI:   GL_SHADING_LANGUAGE_VERSION: OpenGL ES GLSL 1.00 (WebGL)
[2015.02.24-23.15.49:079][  0]LogRHI: OpenGL Extensions:
[2015.02.24-23.15.49:081][  0]LogRHI:   ANGLE_instanced_arrays
[2015.02.24-23.15.49:083][  0]LogRHI:   GL_ANGLE_instanced_arrays
[2015.02.24-23.15.49:085][  0]LogRHI:   EXT_blend_minmax
[2015.02.24-23.15.49:087][  0]LogRHI:   GL_EXT_blend_minmax
[2015.02.24-23.15.49:089][  0]LogRHI:   EXT_frag_depth
[2015.02.24-23.15.49:092][  0]LogRHI:   GL_EXT_frag_depth
[2015.02.24-23.15.49:095][  0]LogRHI:   EXT_shader_texture_lod
[2015.02.24-23.15.49:098][  0]LogRHI:   GL_EXT_shader_texture_lod
[2015.02.24-23.15.49:101][  0]LogRHI:   EXT_texture_filter_anisotropic
[2015.02.24-23.15.49:104][  0]LogRHI:   GL_EXT_texture_filter_anisotropic
[2015.02.24-23.15.49:106][  0]LogRHI:   OES_element_index_uint
[2015.02.24-23.15.49:109][  0]LogRHI:   GL_OES_element_index_uint
[2015.02.24-23.15.49:112][  0]LogRHI:   OES_standard_derivatives
[2015.02.24-23.15.49:115][  0]LogRHI:   GL_OES_standard_derivatives
[2015.02.24-23.15.49:118][  0]LogRHI:   OES_texture_float
[2015.02.24-23.15.49:120][  0]LogRHI:   GL_OES_texture_float
[2015.02.24-23.15.49:122][  0]LogRHI:   OES_texture_float_linear
[2015.02.24-23.15.49:125][  0]LogRHI:   GL_OES_texture_float_linear
[2015.02.24-23.15.49:127][  0]LogRHI:   OES_texture_half_float
[2015.02.24-23.15.49:129][  0]LogRHI:   GL_OES_texture_half_float
[2015.02.24-23.15.49:132][  0]LogRHI:   OES_texture_half_float_linear
[2015.02.24-23.15.49:137][  0]LogRHI:   GL_OES_texture_half_float_linear
[2015.02.24-23.15.49:141][  0]LogRHI:   OES_vertex_array_object
[2015.02.24-23.15.49:144][  0]LogRHI:   GL_OES_vertex_array_object
[2015.02.24-23.15.49:147][  0]LogRHI:   WEBGL_color_buffer_float
[2015.02.24-23.15.49:150][  0]LogRHI:   GL_WEBGL_color_buffer_float
[2015.02.24-23.15.49:157][  0]LogRHI:   WEBGL_compressed_texture_s3tc
[2015.02.24-23.15.49:159][  0]LogRHI:   GL_WEBGL_compressed_texture_s3tc
[2015.02.24-23.15.49:162][  0]LogRHI:   WEBGL_depth_texture
[2015.02.24-23.15.49:164][  0]LogRHI:   GL_WEBGL_depth_texture
[2015.02.24-23.15.49:166][  0]LogRHI:   WEBGL_draw_buffers
[2015.02.24-23.15.49:168][  0]LogRHI:   GL_WEBGL_draw_buffers
[2015.02.24-23.15.49:170][  0]LogRHI:   WEBGL_lose_context
[2015.02.24-23.15.49:173][  0]LogRHI:   GL_WEBGL_lose_context
[2015.02.24-23.15.49:175][  0]LogRHI:   MOZ_WEBGL_lose_context
[2015.02.24-23.15.49:177][  0]LogRHI:   GL_MOZ_WEBGL_lose_context
[2015.02.24-23.15.49:180][  0]LogRHI:   MOZ_WEBGL_compressed_texture_s3tc
[2015.02.24-23.15.49:182][  0]LogRHI:   GL_MOZ_WEBGL_compressed_texture_s3tc
[2015.02.24-23.15.49:184][  0]LogRHI:   MOZ_WEBGL_depth_texture
[2015.02.24-23.15.49:186][  0]LogRHI:   GL_MOZ_WEBGL_depth_texture
[2015.02.24-23.15.49:190][  0]LogRHI:   GL_MAX_VERTEX_UNIFORM_VECTORS: 1024
[2015.02.24-23.15.49:193][  0]LogRHI:   GL_MAX_FRAGMENT_UNIFORM_VECTORS: 1024
[2015.02.24-23.15.49:201][  0]LogRHI: Fragment shader lowp precision: 23
[2015.02.24-23.15.49:203][  0]LogRHI: Fragment shader mediump precision: 23
[2015.02.24-23.15.49:205][  0]LogRHI: Fragment shader highp precision: 23
[2015.02.24-23.15.49:207][  0]LogRHI:   GL_MAX_TEXTURE_SIZE: 16384
[2015.02.24-23.15.49:210][  0]LogRHI:   GL_MAX_CUBE_MAP_TEXTURE_SIZE: 16384
[2015.02.24-23.15.49:213][  0]LogRHI:   GL_MAX_RENDERBUFFER_SIZE: 16384
[2015.02.24-23.15.49:216][  0]LogRHI:   GL_MAX_TEXTURE_IMAGE_UNITS: 16
[2015.02.24-23.15.49:219][  0]LogRHI:   GL_MAX_COLOR_ATTACHMENTS: 1
[2015.02.24-23.15.49:222][  0]LogRHI:   GL_MAX_SAMPLES: 1
[2015.02.24-23.15.49:225][  0]LogRHI:   GL_MAX_COLOR_TEXTURE_SAMPLES: 1
[2015.02.24-23.15.49:228][  0]LogRHI:   GL_MAX_DEPTH_TEXTURE_SAMPLES: 1
[2015.02.24-23.15.49:231][  0]LogRHI:   GL_MAX_INTEGER_SAMPLES: 1
[2015.02.24-23.15.49:234][  0]LogRHI:   GL_MAX_COMBINED_TEXTURE_IMAGE_UNITS: 32
[2015.02.24-23.15.49:237][  0]LogRHI:   GL_MAX_VERTEX_ATTRIBS: 16
[2015.02.24-23.15.49:240][  0]LogRHI:   GL_MAX_TEXTURE_MAX_ANISOTROPY_EXT: 16
[2015.02.24-23.15.49:243][  0]LogRHI: OpenGL MajorVersion = 2, MinorVersion = 0, ShaderPlatform = GLSL_ES2_WEBGL, FeatureLevel = ES2
[2015.02.24-23.15.49:270][  0]LogTextLocalizationManager: The requested culture ('en_US') has no localization data; parent culture's ('en') localization data will be used.
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[2015.02.24-23.15.50:140][  0]LogConfig:Warning: Failed to saved backup for config[EditorUserSettings]
[2015.02.24-23.15.50:305][  0]LogObj: 20183 objects as part of root set at end of initial load.
[2015.02.24-23.15.50:308][  0]LogUObjectAllocator: 2963416 out of 0 bytes used by permanent object pool.
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[2015.02.24-23.15.50:312][  0]LogHTML5Launch:Display: PreInit Complete
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[2015.02.24-23.15.50:316][  0]LogHTML5Launch:Display: Init Start
[2015.02.24-23.15.50:321][  0]LogEngine: Initializing Engine...
[2015.02.24-23.15.50:366][  0]LogALAudio: ALAudio device opened : Device
[2015.02.24-23.15.50:369][  0]LogALAudio: AL_VENDOR      : Emscripten
[2015.02.24-23.15.50:371][  0]LogALAudio: AL_RENDERER    : WebAudio
[2015.02.24-23.15.50:373][  0]LogALAudio: AL_VERSION     : 1.1
[2015.02.24-23.15.50:376][  0]LogALAudio: AL_EXTENSIONS  : 
[2015.02.24-23.15.50:380][  0]LogInit: FAudioDevice initialized.
[2015.02.24-23.15.50:382][  0]LogInit: Texture streaming: Disabled
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[2015.02.24-23.15.50:399][  0]LogConfig:Warning: Failed to saved backup for config[GameUserSettings]
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[2015.02.24-23.15.50:412][  0]LogConfig:Warning: Failed to saved backup for config[GameUserSettings]
[2015.02.24-23.15.50:451][  0]LogNet: Browse: /Game/Maps/Menu?Name=Player
[2015.02.24-23.15.50:454][  0]LogLoad: LoadMap: /Game/Maps/Menu?Name=Player
[2015.02.24-23.15.50:475][  0]LogMemory: Platform Memory Stats for HTML5
[2015.02.24-23.15.50:478][  0]LogMemory: Process Physical Memory: 0.00 MB used, 0.00 MB peak
[2015.02.24-23.15.50:481][  0]LogMemory: Process Virtual Memory: 0.00 MB used, 0.00 MB peak
[2015.02.24-23.15.50:484][  0]LogMemory: Physical Memory: 1024.00 MB used, 1024.00 MB total
[2015.02.24-23.15.50:486][  0]LogMemory: Virtual Memory: 0.00 MB used, 0.00 MB total
[2015.02.24-23.15.50:488][  0]LogMemory: 
[2015.02.24-23.15.50:491][  0]Allocator Stats for ANSI: (not implemented)
[2015.02.24-23.15.50:826][  0]LogWorld: Game class is 'GameMode'
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[2015.02.24-23.15.50:843][  0]LogStats:Warning: MetaData mismatch. Did you assign a stat to two groups? New //STATGROUP_Threads//None///Thread_10000_0///////STATCAT_Advanced//// old //STATGROUP_Threads//None///Thread_ffff_0///////STATCAT_Advanced////
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[2015.02.24-23.15.50:848][  0]LogStats:Warning: MetaData mismatch. Did you assign a stat to two groups? New //STATGROUP_Threads//None///Thread_10001_0///////STATCAT_Advanced//// old //STATGROUP_Threads//None///Thread_ffff_0///////STATCAT_Advanced////
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[2015.02.24-23.15.50:866][  0]LogModuleManager:Warning: ModuleManager: Module 'GameplayDebugger' not found - its StaticallyLinkedModuleInitializers function is null.
[2015.02.24-23.15.50:869][  0]LogAIModule: Creating AISystem for world Menu
[2015.02.24-23.15.51:163][  0]LogWorld: Bringing World /Game/Maps/Menu.Menu up for play (max tick rate 0) at 2015.02.24-23.15.51
[2015.02.24-23.15.51:166][  0]LogWorld: Bringing up level for play took: 0.293509
[2015.02.24-23.15.51:172][  0]LogGameMode: Warning - PATHS NOT DEFINED or NO PLAYERSTART with positive rating
[2015.02.24-23.15.51:324][  0]LogBlueprintUserMessages: CurrentMark

https://github.com/EpicGames/UnrealEngine/commit/9cff0ef5001c493be360f53ff647f6ae5c6ed069 Should possibly fix your issue,