Problems updating project to 4.4

In Config\Default Engine it is currently set to .

[/Script/Engine.Engine]
GameViewportClientClassName=/Script/Engine.GameViewportClient
GameViewportClientClassName=/Script/QUBE.QUBEGameViewportClient

The editor will load , but custom game class is missing so none of the blueprints work if it is set to.

[/Script/Engine.Engine]
GameViewportClientClassName=/Script/Engine.GameViewportClient

The editor will crash when loading if it is set to .

[/Script/Engine.Engine]
GameViewportClientClassName=/Script/QUBE.QUBEGameViewportClient

or

[/Script/Engine.Engine]
GameViewportClientClassName=/GameViewportClient

This is the crash log .

!Id:e99b4f2873ddb4e8aaf6e6f43f25976f

Unknown exception - code 00000001 (first/second chance not available)

Assertion failed: GameViewportClientClass != NULL [File:D:\BuildFarm\buildmachine_++depot+UE4-Releases+4.4\Engine\Source\Runtime\Engine\Private\UnrealEngine.cpp] [Line: 1322]
Engine config value GameViewportClientClassName is not a valid class n