Get GameMode from Widget Blueprint (UMG)

Hi,
I would like to Get Game Mode from Widget Blueprint but I receive error. Could you help me?

Fatal error: [File:D:\Epic Games\4.5\Engine\Source\Editor\UnrealEd\Private\Editor.cpp] [Line: 6846] 
World /Game/Maps/UEDPIE_0_MainMenu.MainMenu not cleaned up by garbage collection!
   (Object is not currently rooted)


KERNELBASE.dll!UnknownFunction (0x00007ffb145f606c) + 0 bytes [UnknownFile:0]
UE4Editor-Core.dll!FOutputDeviceWindowsError::Serialize() (0x00007ffafaf29edd) + 0 bytes [d:\epic games\4.5\engine\source\runtime\core\private\windows\windowsplatformoutputdevices.cpp:95]
UE4Editor-Core.dll!FMsg::Logf__VA() (0x00007ffafadc59ef) + 0 bytes [d:\epic games\4.5\engine\source\runtime\core\private\misc\outputdevice.cpp:522]
UE4Editor-UnrealEd.dll!UEditorEngine::VerifyLoadMapWorldCleanup() (0x00007ffaeed5a174) + 127 bytes [d:\epic games\4.5\engine\source\editor\unrealed\private\editor.cpp:6846]
UE4Editor-Engine.dll!UEngine::LoadMap() (0x00007ffaf07877da) + 0 bytes [d:\epic games\4.5\engine\source\runtime\engine\private\unrealengine.cpp:8461]
UE4Editor-Engine.dll!UEngine::Browse() (0x00007ffaf07307b0) + 41 bytes [d:\epic games\4.5\engine\source\runtime\engine\private\unrealengine.cpp:7874]
UE4Editor-Engine.dll!UEngine::TickWorldTravel() (0x00007ffaf07afd5d) + 63 bytes [d:\epic games\4.5\engine\source\runtime\engine\private\unrealengine.cpp:8040]
UE4Editor-UnrealEd.dll!UEditorEngine::Tick() (0x00007ffaeed56588) + 0 bytes [d:\epic games\4.5\engine\source\editor\unrealed\private\editor.cpp:1162]
UE4Editor-UnrealEd.dll!UUnrealEdEngine::Tick() (0x00007ffaef1af966) + 0 bytes [d:\epic games\4.5\engine\source\editor\unrealed\private\unrealedengine.cpp:278]
UE4Editor.exe!FEngineLoop::Tick() (0x00007ff7707ab224) + 0 bytes [d:\epic games\4.5\engine\source\runtime\launch\private\launchengineloop.cpp:2129]
UE4Editor.exe!GuardedMain() (0x00007ff7707a0c3e) + 0 bytes [d:\epic games\4.5\engine\source\runtime\launch\private\launch.cpp:133]
UE4Editor.exe!GuardedMainWrapper() (0x00007ff7707a0caa) + 5 bytes [d:\epic games\4.5\engine\source\runtime\launch\private\windows\launchwindows.cpp:125]
UE4Editor.exe!WinMain() (0x00007ff7707ac859) + 17 bytes [d:\epic games\4.5\engine\source\runtime\launch\private\windows\launchwindows.cpp:201]
UE4Editor.exe!__tmainCRTStartup() (0x00007ff7707ad789) + 21 bytes [f:\dd\vctools\crt\crtw32\dllstuff\crtexe.c:618]
KERNEL32.DLL!UnknownFunction (0x00007ffb153816ad) + 0 bytes [UnknownFile:0]
ntdll.dll!UnknownFunction (0x00007ffb170f4409) + 0 bytes [UnknownFile:0]
ntdll.dll!UnknownFunction (0x00007ffb170f4409) + 0 bytes [UnknownFile:0]

You need to remove all your widget from the viewport before you can Open a Level. Thats a known ‘bug’.