Opening widget blueprint causes editor to crash

Assertion failed: IsValid() [File:C:\Unreal45\Unreal\Engine\Source\Runtime\Core\Public\Templates\SharedPointer.h] [Line: 658] 
 
 
 KERNELBASE.dll!UnknownFunction (0x000007fefd93940d) + 0 bytes [UnknownFile:0]
UE4Editor-Core.dll!FOutputDeviceWindowsError::Serialize() (0x000007fede5b9ecd) + 0 bytes [c:\unreal45\unreal\engine\source\runtime\core\private\windows\windowsplatformoutputdevices.cpp:95]
UE4Editor-Core.dll!FOutputDevice::Logf__VA() (0x000007fede455b08) + 159 bytes [c:\unreal45\unreal\engine\source\runtime\core\private\misc\outputdevice.cpp:145]
UE4Editor-Core.dll!FDebug::AssertFailed() (0x000007fede4388c2) + 62 bytes [c:\unreal45\unreal\engine\source\runtime\core\private\misc\outputdevice.cpp:220]
UE4Editor-UMGEditor.dll!FWidgetBlueprintEditor::InitWidgetBlueprintEditor() (0x000007fed4cedb8e) + 44 bytes [c:\unreal45\unreal\engine\source\editor\umgeditor\private\widgetblueprinteditor.cpp:67]
UE4Editor-UMGEditor.dll!FAssetTypeActions_WidgetBlueprint::OpenAssetEditor() (0x000007fed4d11df1) + 24 bytes [c:\unreal45\unreal\engine\source\editor\umgeditor\private\assettypeactions_widgetblueprint.cpp:32]
UE4Editor-UnrealEd.dll!FAssetEditorManager::OpenEditorForAsset() (0x000007fed9ac61e2) + 152 bytes [c:\unreal45\unreal\engine\source\editor\unrealed\private\toolkits\asseteditormanager.cpp:288]
UE4Editor-UMGEditor.dll!FAssetTypeActions_Base::AssetsActivated() (0x000007fed4c800c9) + 0 bytes [c:\unreal45\unreal\engine\source\developer\assettools\public\assettypeactions_base.h:36]
UE4Editor-ContentBrowser.dll!SContentBrowser::OnAssetsActivated() (0x000007feceaac3c4) + 0 bytes [c:\unreal45\unreal\engine\source\editor\contentbrowser\private\scontentbrowser.cpp:1362]
UE4Editor-ContentBrowser.dll!TBaseSPMethodDelegateInstance_TwoParams<SContentBrowser,void,TArray<FAssetData,FDefaultAllocator> const & __ptr64,enum EAssetTypeActivationMethod::Type,0>::Execute() (0x000007fecea38163) + 18 bytes [c:\unreal45\unreal\engine\source\runtime\core\public\delegates\delegateinstancesimpl.inl:161]
UE4Editor-ContentBrowser.dll!TBaseSPMethodDelegateInstance_TwoParams<SContentBrowser,void,TArray<FAssetData,FDefaultAllocator> const & __ptr64,enum EAssetTypeActivationMethod::Type,0>::ExecuteIfSafe() (0x000007fecea41d08) + 15 bytes [c:\unreal45\unreal\engine\source\runtime\core\public\delegates\delegateinstancesimpl.inl:171]
UE4Editor-ContentBrowser.dll!SAssetView::OnListMouseButtonDoubleClick() (0x000007feceab7e04) + 43 bytes [c:\unreal45\unreal\engine\source\editor\contentbrowser\private\sassetview.cpp:3125]
UE4Editor-ContentBrowser.dll!TBaseSPMethodDelegateInstance_OneParam<SAssetView,void,TSharedPtr<FAssetViewItem,0>,0>::Execute() (0x000007fecea314b6) + 41 bytes [c:\unreal45\unreal\engine\source\runtime\core\public\delegates\delegateinstancesimpl.inl:161]
UE4Editor-ContentBrowser.dll!TBaseSPMethodDelegateInstance_OneParam<SAssetView,void,TSharedPtr<FAssetViewItem,0>,0>::ExecuteIfSafe() (0x000007fecea3fd6b) + 38 bytes [c:\unreal45\unreal\engine\source\runtime\core\public\delegates\delegateinstancesimpl.inl:171]
UE4Editor-ContentBrowser.dll!TBaseDelegate_OneParam<void,TSharedPtr<FAssetViewItem,0> >::ExecuteIfBound() (0x000007fecea3d456) + 38 bytes [c:\unreal45\unreal\engine\source\runtime\core\public\delegates\delegatesignatureimpl.inl:1072]
UE4Editor-ContentBrowser.dll!SListView<TSharedPtr<FAssetViewItem,0> >::Private_OnItemDoubleClicked() (0x000007feceaccabf) + 41 bytes [c:\unreal45\unreal\engine\source\runtime\slate\public\widgets\views\slistview.h:687]
UE4Editor-ContentBrowser.dll!STableRow<TSharedPtr<FAssetViewItem,0> >::OnMouseButtonDoubleClick() (0x000007feceab804f) + 0 bytes [c:\unreal45\unreal\engine\source\runtime\slate\public\widgets\views\stablerow.h:180]
UE4Editor-Slate.dll!FSlateApplication::ProcessMouseButtonDoubleClickEvent() (0x000007fedb10d705) + 30 bytes [c:\unreal45\unreal\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:3436]
UE4Editor-Slate.dll!FSlateApplication::OnMouseDoubleClick() (0x000007fedb0fb36b) + 19 bytes [c:\unreal45\unreal\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:3413]
UE4Editor-Core.dll!FWindowsApplication::ProcessDeferredMessage() (0x000007fede539aac) + 32 bytes [c:\unreal45\unreal\engine\source\runtime\core\private\windows\windowsapplication.cpp:1288]
UE4Editor-Core.dll!FWindowsApplication::DeferMessage() (0x000007fede5260db) + 74 bytes [c:\unreal45\unreal\engine\source\runtime\core\private\windows\windowsapplication.cpp:1637]
UE4Editor-Core.dll!FWindowsApplication::ProcessMessage() (0x000007fede53adb9) + 41 bytes [c:\unreal45\unreal\engine\source\runtime\core\private\windows\windowsapplication.cpp:737]
UE4Editor-Core.dll!FWindowsApplication::AppWndProc() (0x000007fede522a22) + 0 bytes [c:\unreal45\unreal\engine\source\runtime\core\private\windows\windowsapplication.cpp:599]
USER32.dll!UnknownFunction (0x00000000779d9bd1) + 0 bytes [UnknownFile:0]
USER32.dll!UnknownFunction (0x00000000779d98da) + 0 bytes [UnknownFile:0]
UE4Editor-Core.dll!FWindowsPlatformMisc::PumpMessages() (0x000007fede53b276) + 48 bytes [c:\unreal45\unreal\engine\source\runtime\core\private\windows\windowsplatformmisc.cpp:757]
UE4Editor.exe!FEngineLoop::Tick() (0x000000013fceb082) + 8 bytes [c:\unreal45\unreal\engine\source\runtime\launch\private\launchengineloop.cpp:2111]
UE4Editor.exe!GuardedMain() (0x000000013fce0c3e) + 0 bytes [c:\unreal45\unreal\engine\source\runtime\launch\private\launch.cpp:133]
UE4Editor.exe!GuardedMainWrapper() (0x000000013fce0caa) + 5 bytes [c:\unreal45\unreal\engine\source\runtime\launch\private\windows\launchwindows.cpp:125]
UE4Editor.exe!WinMain() (0x000000013fcec859) + 17 bytes [c:\unreal45\unreal\engine\source\runtime\launch\private\windows\launchwindows.cpp:201]
UE4Editor.exe!__tmainCRTStartup() (0x000000013fced789) + 21 bytes [f:\dd\vctools\crt\crtw32\dllstuff\crtexe.c:618]
kernel32.dll!UnknownFunction (0x00000000778b59ed) + 0 bytes [UnknownFile:0]
ntdll.dll!UnknownFunction (0x0000000077aec541) + 0 bytes [UnknownFile:0]
ntdll.dll!UnknownFunction (0x0000000077aec541) + 0 bytes [UnknownFile:0]