Engine started to throw the error, When I started WBP creation

[anonymous_user_b1499ca2]

What’s wrong?
Do some of my properties are incorrect?
I have also encountered the problem with new map saving ( it says, N map failed to save and suggest me to try again/ cancel and something else);

Error Message:

[2020.02.19-10.01.41:542][450]LogFileHelpers: Saving map ‘TutorialMap’ took 0.258
The thread 0x22c4 has exited with code 0 (0x0).
[2020.02.19-10.03.01:177][750]LogSlate: Took 0.000129 seconds to synchronously load lazily loaded font ‘…/…/…/Engine/Content/Slate/Fonts/Roboto-BoldCondensedItalic.ttf’ (160K)
[2020.02.19-10.03.08:407][616]BlueprintLog: New page: Compile WBP_TutorialGuide
[2020.02.19-10.03.08:453][616]LogUObjectHash: Compacting FUObjectHashTables data took 4.71ms
[2020.02.19-10.03.08:469][616]Cmd: OBJ SAVEPACKAGE PACKAGE=“/Game/Blueprints/Tutorial/WBP_TutorialGuide” FILE=“G:/Documents/Unreal Projects/CoopGame/Content/Blueprints/Tutorial/WBP_TutorialGuide.uasset” SILENT=true
[2020.02.19-10.03.08:484][616]LogSavePackage: Moving ‘G:/Documents/Unreal Projects/CoopGame/Saved/WBP_TutorialGuide0EA43EF340830914BEF577A1B3AC6304.tmp’ to ‘G:/Documents/Unreal Projects/CoopGame/Content/Blueprints/Tutorial/WBP_TutorialGuide.uasset’
[2020.02.19-10.03.11:824] 12]LogUObjectBase: Warning: Object is not registered
[2020.02.19-10.03.11:824] 12]LogOutputDevice: Warning:

Ensure condition failed: false [File:D:/Build/++UE4/Sync/Engine/Source/Editor/UnrealEd/Private/Kismet2/KismetDebugUtilities.cpp] [Line: 1154]
Error: Invalid (but non-null) property associated with pin; cannot get variable value
[2020.02.19-10.03.11:824] 12]LogOutputDevice: Error: Ensure condition failed: false [File:D:/Build/++UE4/Sync/Engine/Source/Editor/UnrealEd/Private/Kismet2/KismetDebugUtilities.cpp] [Line: 1154]
Error: Invalid (but non-null) property associated with pin; cannot get variable value

[2020.02.19-10.03.11:824] 12]LogStats: FDebug::EnsureFailed - 0.000 s
UE4Editor.exe has triggered a breakpoint.