Inserting before a FSlateImageRun twice will cause crash

1. Create an empty project.
2. Create a UMG widget with a RichTextBox and insert an image tag to have a slate image run
3. Place the cursor in front of the slate image run
4. Copy some text to the clipboard.
5. Ctrl + V: Paste the text+* in front of the slate image run*+.
6. Ctrl + V: Paste Again

will fail the following check:
checkf(RunRange.Len() == 1, TEXT("Debug Source: %s"), *DebugSourceInfo.Get(FString()));

[2019.04.12-01.56.33:161][468]LogWindows: Error: === Critical error: ===
[2019.04.12-01.56.33:161][468]LogWindows: Error:
[2019.04.12-01.56.33:161][468]LogWindows: Error: Assertion failed: RunRange.Len() == 1 [Link Removed] [Line: 1659]
[2019.04.12-01.56.33:161][468]LogWindows: Error: Debug Source: NewWidgetBlueprint [NativeWidgetHost_0(MyBlueprintFunctionLibrary.cpp(29))]
[2019.04.12-01.56.33:161][468]LogWindows: Error:
[2019.04.12-01.56.33:161][468]LogWindows: Error:
[2019.04.12-01.56.33:161][468]LogWindows: Error: [Callstack] 0x00007fff147aa388 KERNELBASE.dll!UnknownFunction []
[2019.04.12-01.56.33:161][468]LogWindows: Error: [Callstack] 0x00007ffec6fd1ee7 UE4Editor-Core.dll!ReportAssert() [c:\users\txl\release\engine\source\runtime\core\private\windows\windowsplatformcrashcontext.cpp:553]
[2019.04.12-01.56.33:161][468]LogWindows: Error: [Callstack] 0x00007ffec6fd4697 UE4Editor-Core.dll!FWindowsErrorOutputDevice::Serialize() [c:\users\txl\release\engine\source\runtime\core\private\windows\windowserroroutputdevice.cpp:79]
[2019.04.12-01.56.33:161][468]LogWindows: Error: [Callstack] 0x00007ffec6de7cea UE4Editor-Core.dll!FOutputDevice::LogfImpl() [c:\users\txl\release\engine\source\runtime\core\private\misc\outputdevice.cpp:71]
[2019.04.12-01.56.33:161][468]LogWindows: Error: [Callstack] 0x00007ffec6d6fe07 UE4Editor-Core.dll!FDebug::AssertFailed() [c:\users\txl\release\engine\source\runtime\core\private\misc\assertionmacros.cpp:440]
[2019.04.12-01.56.33:161][468]LogWindows: Error: [Callstack] 0x00007ffec6d70499 UE4Editor-Core.dll!FDebug::CheckVerifyFailedImpl() [c:\users\txl\release\engine\source\runtime\core\private\misc\assertionmacros.cpp:418]
[2019.04.12-01.56.33:162][468]LogWindows: Error: [Callstack] 0x00007ffecda5df63 UE4Editor-Slate.dll!DispatchCheckVerify<void,<lambda_6896d220161c19d6a8f55623f3ca775d> >() [c:\users\txl\release\engine\source\runtime\core\public\misc\assertionmacros.h:161]
[2019.04.12-01.56.33:162][468]LogWindows: Error: [Callstack] 0x00007ffecd8c8d60 UE4Editor-Slate.dll!FTextLayout::InsertAt() [c:\users\txl\release\engine\source\runtime\slate\private\framework\text\textlayout.cpp:1659]
[2019.04.12-01.56.33:162][468]LogWindows: Error: [Callstack] 0x00007ffecd9a0766 UE4Editor-Slate.dll!FSlateEditableTextLayout::InsertTextAtCursorImpl() [c:\users\txl\release\engine\source\runtime\slate\private\widgets\text\slateeditabletextlayout.cpp:1899]
[2019.04.12-01.56.33:162][468]LogWindows: Error: [Callstack] 0x00007ffecd9a7c16 UE4Editor-Slate.dll!FSlateEditableTextLayout::PasteTextFromClipboard() [c:\users\txl\release\engine\source\runtime\slate\private\widgets\text\slateeditabletextlayout.cpp:1822]
[2019.04.12-01.56.33:162][468]LogWindows: Error: [Callstack] 0x00007ffecd996f0e UE4Editor-Slate.dll!TBaseRawMethodDelegateInstance<0,FSlateEditableTextLayout,void __cdecl(void)>::ExecuteIfSafe() [c:\users\txl\release\engine\source\runtime\core\public\delegates\delegateinstancesimpl.h:518]
[2019.04.12-01.56.33:162][468]LogWindows: Error: [Callstack] 0x00007ffecd7571ea UE4Editor-Slate.dll!FUICommandList::ConditionalProcessCommandBindings() [c:\users\txl\release\engine\source\runtime\slate\private\framework\commands\uicommandlist.cpp:217]
[2019.04.12-01.56.33:162][468]LogWindows: Error: [Callstack] 0x00007ffecd7873fe UE4Editor-Slate.dll!FUICommandList::ProcessCommandBindings() [c:\users\txl\release\engine\source\runtime\slate\private\framework\commands\uicommandlist.cpp:161]
[2019.04.12-01.56.33:162][468]LogWindows: Error: [Callstack] 0x00007ffecd99e086 UE4Editor-Slate.dll!FSlateEditableTextLayout::HandleKeyDown() [c:\users\txl\release\engine\source\runtime\slate\private\widgets\text\slateeditabletextlayout.cpp:1044]
[2019.04.12-01.56.33:162][468]LogWindows: Error: [Callstack] 0x00007ffecd9a3a9d UE4Editor-Slate.dll!SMultiLineEditableText::OnKeyDown() [c:\users\txl\release\engine\source\runtime\slate\private\widgets\text\smultilineeditabletext.cpp:607]
[2019.04.12-01.56.33:162][468]LogWindows: Error: [Callstack] 0x00007ffecd721e66 UE4Editor-Slate.dll!FEventRouter::Route<FReply,FEventRouter::FBubblePolicy,FKeyEvent,<lambda_21fddcfe5d8b6e57b707a8971995adc5> >() [c:\users\txl\release\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:271]
[2019.04.12-01.56.33:162][468]LogWindows: Error: [Callstack] 0x00007ffecd788d8d UE4Editor-Slate.dll!FSlateApplication::ProcessKeyDownEvent() [c:\users\txl\release\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:5134]
[2019.04.12-01.56.33:162][468]LogWindows: Error: [Callstack] 0x00007ffecd77f18e UE4Editor-Slate.dll!FSlateApplication::OnKeyDown() [c:\users\txl\release\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:5042]
[2019.04.12-01.56.33:162][468]LogWindows: Error: [Callstack] 0x00007ffefaffb55a UE4Editor-ApplicationCore.dll!FWindowsApplication::ProcessDeferredMessage() [c:\users\txl\release\engine\source\runtime\applicationcore\private\windows\windowsapplication.cpp:1677]
[2019.04.12-01.56.33:162][468]LogWindows: Error: [Callstack] 0x00007ffefafeef9f UE4Editor-ApplicationCore.dll!FWindowsApplication::DeferMessage() [c:\users\txl\release\engine\source\runtime\applicationcore\private\windows\windowsapplication.cpp:2292]
[2019.04.12-01.56.33:162][468]LogWindows: Error: [Callstack] 0x00007ffefaffd77f UE4Editor-ApplicationCore.dll!FWindowsApplication::ProcessMessage() [c:\users\txl\release\engine\source\runtime\applicationcore\private\windows\windowsapplication.cpp:1522]
[2019.04.12-01.56.33:162][468]LogWindows: Error: [Callstack] 0x00007ffefafec090 UE4Editor-ApplicationCore.dll!FWindowsApplication::AppWndProc() [c:\users\txl\release\engine\source\runtime\applicationcore\private\windows\windowsapplication.cpp:772]
[2019.04.12-01.56.33:162][468]LogWindows: Error: [Callstack] 0x00007fff17ab6d41 USER32.dll!UnknownFunction []
[2019.04.12-01.56.33:162][468]LogWindows: Error: [Callstack] 0x00007fff17ab6713 USER32.dll!UnknownFunction []
[2019.04.12-01.56.33:162][468]LogWindows: Error: [Callstack] 0x00007ffefaffe946 UE4Editor-ApplicationCore.dll!FWindowsPlatformApplicationMisc::PumpMessages() [c:\users\txl\release\engine\source\runtime\applicationcore\private\windows\windowsplatformapplicationmisc.cpp:130]
[2019.04.12-01.56.33:162][468]LogWindows: Error: [Callstack] 0x00007ff61dbe5d3e UE4Editor.exe!FEngineLoop::Tick() [c:\users\txl\release\engine\source\runtime\launch\private\launchengineloop.cpp:3882]
[2019.04.12-01.56.33:162][468]LogWindows: Error: [Callstack] 0x00007ff61dbf554c UE4Editor.exe!GuardedMain() [c:\users\txl\release\engine\source\runtime\launch\private\launch.cpp:168]
[2019.04.12-01.56.33:162][468]LogWindows: Error: [Callstack] 0x00007ff61dbf55ca UE4Editor.exe!GuardedMainWrapper() [c:\users\txl\release\engine\source\runtime\launch\private\windows\launchwindows.cpp:145]
[2019.04.12-01.56.33:162][468]LogWindows: Error: [Callstack] 0x00007ff61dc0315c UE4Editor.exe!WinMain() [c:\users\txl\release\engine\source\runtime\launch\private\windows\launchwindows.cpp:275]
[2019.04.12-01.56.33:162][468]LogWindows: Error: [Callstack] 0x00007ff61dc05b7e UE4Editor.exe!__scrt_common_main_seh() [d:\agent\_work\1\s\src\vctools\crt\vcstartup\src\startup\exe_common.inl:288]
[2019.04.12-01.56.33:162][468]LogWindows: Error: [Callstack] 0x00007fff157b4034 KERNEL32.DLL!UnknownFunction []
[2019.04.12-01.56.33:162][468]LogWindows: Error: [Callstack] 0x00007fff17d03691 ntdll.dll!UnknownFunction []
[2019.04.12-01.56.33:162][468]LogWindows: Error:
[2019.04.12-01.56.33:174][468]LogExit: Executing StaticShutdownAfterError
[2019.04.12-01.56.33:178][468]LogWindows: FPlatformMisc::RequestExit(1)
[2019.04.12-01.56.33:190][468]Log file closed, 04/12/19 09:56:33