[CrashReport] UE4Editor_SlateCore!SWidget::ExecuteActiveTimers() [swidget.cpp:986]

right mouse button in material editor made engine crash....becomes slow and crash....64gb ram, 2 xeon and gtx690....need to restart computer to everything works fine. need a solution to this...

Assertion failed: (Index >= 0) & (Index < ArrayNum) [File:D:\Build\++UE4+Release-4.17+Compile\Sync\Engine\Source\Runtime\Core\Public\Containers/Array.h] [Line: 596] Array index out of bounds: 0 from an array of size 0

UE4Editor_SlateCore!SWidget::ExecuteActiveTimers() [swidget.cpp:986]
UE4Editor_SlateCore!SWidget::Paint() [swidget.cpp:855]
UE4Editor_SlateCore!SOverlay::OnPaint() [soverlay.cpp:97]
UE4Editor_SlateCore!SWidget::Paint() [swidget.cpp:885]
UE4Editor_SlateCore!SPanel::PaintArrangedChildren() [spanel.cpp:31]
UE4Editor_SlateCore!SPanel::OnPaint() [spanel.cpp:12]
UE4Editor_SlateCore!SWidget::Paint() [swidget.cpp:885]
UE4Editor_SlateCore!SPanel::PaintArrangedChildren() [spanel.cpp:31]
UE4Editor_SlateCore!SPanel::OnPaint() [spanel.cpp:12]
UE4Editor_SlateCore!SWidget::Paint() [swidget.cpp:885]
UE4Editor_SlateCore!SPanel::PaintArrangedChildren() [spanel.cpp:31]
UE4Editor_SlateCore!SPanel::OnPaint() [spanel.cpp:12]
UE4Editor_SlateCore!SWidget::Paint() [swidget.cpp:885]
UE4Editor_SlateCore!SOverlay::OnPaint() [soverlay.cpp:97]
UE4Editor_SlateCore!SWidget::Paint() [swidget.cpp:885]
UE4Editor_SlateCore!SPanel::PaintArrangedChildren() [spanel.cpp:31]
UE4Editor_SlateCore!SPanel::OnPaint() [spanel.cpp:12]
UE4Editor_SlateCore!SWidget::Paint() [swidget.cpp:885]
UE4Editor_SlateCore!SCompoundWidget::OnPaint() [scompoundwidget.cpp:35]
UE4Editor_Slate!SScrollBox::OnPaint() [sscrollbox.cpp:980]
UE4Editor_SlateCore!SWidget::Paint() [swidget.cpp:885]
UE4Editor_SlateCore!SCompoundWidget::OnPaint() [scompoundwidget.cpp:35]
UE4Editor_Slate!SBorder::OnPaint() [sborder.cpp:85]
UE4Editor_SlateCore!SWidget::Paint() [swidget.cpp:885]
UE4Editor_SlateCore!SCompoundWidget::OnPaint() [scompoundwidget.cpp:35]
UE4Editor_SlateCore!SWidget::Paint() [swidget.cpp:885]
UE4Editor_SlateCore!FSlateWindowElementList::FDeferredPaint::ExecutePaint() [drawelements.cpp:830]
UE4Editor_SlateCore!FSlateWindowElementList::PaintDeferred() [drawelements.cpp:855]
UE4Editor_SlateCore!SWidget::Paint() [swidget.cpp:944]
UE4Editor_Slate!FSlateApplication::DrawWindowAndChildren() [slateapplication.cpp:1231]
UE4Editor_Slate!FSlateApplication::DrawWindowAndChildren() [slateapplication.cpp:1320]
UE4Editor_Slate!FSlateApplication::DrawWindowAndChildren() [slateapplication.cpp:1320]
UE4Editor_Slate!FSlateApplication::PrivateDrawWindows() [slateapplication.cpp:1471]
UE4Editor_Slate!FSlateApplication::DrawWindows() [slateapplication.cpp:1188]
UE4Editor_Slate!FSlateApplication::TickApplication() [slateapplication.cpp:1773]
UE4Editor_Slate!FSlateApplication::Tick() [slateapplication.cpp:1591]
UE4Editor!FEngineLoop::Tick() [launchengineloop.cpp:3278]
UE4Editor!GuardedMain() [launch.cpp:166]
UE4Editor!GuardedMainWrapper() [launchwindows.cpp:134]
UE4Editor!WinMain() [launchwindows.cpp:210]
UE4Editor!__scrt_common_main_seh() [exe_common.inl:253]
kernel32!BaseThreadInitThunk()
ntdll!RtlUserThreadStart()