deleting interface pointer, and clearing interface widget.

6.09.17-00.47.27:445][ 47]LogLinux: === Critical error: === Unhandled Exception: SIGSEGV: invalid attempt to access memory at address 0x00000000

[2016.09.17-00.47.27:445][47]LogLinux: Fatal error!

[Callstack]  00  0x00007f36ca30877f FLinuxPlatformStackWalk::CaptureStackBackTrace(unsigned long long*, unsigned int, void*)
[Callstack]  01  0x00007f36ca1e5775 FGenericPlatformStackWalk::StackWalkAndDump(char*,unsigned long, int, void*)
[Callstack]  02  0x00007f36ca2c71a1 FLinuxCrashContext::CaptureStackTrace()
[Callstack]  03  0x00007f36bf508480 CommonLinuxCrashHandler(FGenericCrashContext const&)
[Callstack]  04  0x00007f36ca2cba14 PlatformCrashHandler(int, siginfo_t*,void*)
[Callstack]  05  0x00007f36cb154080 /usr/lib/libpthread.so.0(+0x11080) [0x7f36cb154080]
[Callstack]  06  0x00007f36ca54818f /opt/unreal-engine/Engine/Binaries/Linux/libUE4Editor-Core.so(+0x60418f) [0x7f36ca54818f]
[Callstack]  07  0x00007f36ca562b4f /opt/unreal-engine/Engine/Binaries/Linux/libUE4Editor-Core.so(+0x61eb4f) [0x7f36ca562b4f]
[Callstack]  08  0x00007f36ca53c5ad /opt/unreal-engine/Engine/Binaries/Linux/libUE4Editor-Core.so(je_realloc+0x14d)
[0x7f36ca53c5ad]
[Callstack]  09  0x00007f36c789dd80 TArray<TSharedPtr<ISceneViewExtension,(ESPMode)1>, FDefaultAllocator>::ResizeForCopy(int,int)
[Callstack]  10  0x00007f36b020cee4 FSceneRenderer::FSceneRenderer(FSceneViewFamily const*, FHitProxyConsumer*)
[Callstack]  11  0x00007f36afd4136c FDeferredShadingSceneRenderer::FDeferredShadingSceneRenderer(FSceneViewFamily const*, FHitProxyConsumer*)
[Callstack]  12  0x00007f36b0212196 FRendererModule::BeginRenderingViewFamily(FCanvas*,FSceneViewFamily*)
[Callstack]  13  0x00007f36c6f577e1 UGameViewportClient::Draw(FViewport*,FCanvas*)
[Callstack]  14  0x00007f36c78190d2 FViewport::Draw(bool)
[Callstack]  15  0x00007f36c0818e00 UEditorEngine::Tick(float, bool)
[Callstack]  16  0x00007f36c1091530 UUnrealEdEngine::Tick(float, bool)
[Callstack]  17  0x000000000042145a FEngineLoop::Tick() [Runtime/Core/Public/Stats/Stats2.h, line 1673]
[Callstack]  18  0x0000000000425d9a GuardedMain(wchar_t const*) [/opt/unrealengine/Engine/Source/Runtime/Launch/Private/Launch.cpp, line 156]
[Callstack]  19  0x00007f36bf508dfb CommonLinuxMain(int, char**, int(*)(wchar_t const*))
[Callstack]  20  0x00007f36bea56291 /usr/lib/libc.so.6(__libc_start_main+0xf1) [0x7f36bea56291]
[Callstack]  21  0x0000000000413f0a /opt/unreal-engine/Engine/Binaries/Linux/UE4Editor(_start+0x2a) [0x413f0a]