Editor crash when disabling looping in a nested subscene

Disabling looping in a nested subsequence seems to crash the editor

upd. Regression was checked on //UE4/Release-4.26 CL 15973114, the issue wasn't reproduced. Regression - Yes

1. Create three level sequences, a master sequence, a shot sequence and a sub sequence
2. Add the shot sequence as a shot to the master sequence
3. Add the sub sequence as a sub sequence to the shot sequence
4. Open the master sequence
5. Double click on the shot section to open the shot
6. Right click on the sub sequence section and enable looping
7. Disable looping

RESULT:

The editor will crash 

> UE4Editor-Sequencer-Win64-Debug.dll!FMovieSceneSequenceTransform::InverseFromWarp(const TArrayView<unsigned int const ,int> & WarpCounts) Line 443 C+> UE4Editor-Sequencer-Win64-Debug.dll!FMovieSceneSequenceTransform::InverseFromWarp(const TArrayView<unsigned int const ,int> & WarpCounts) Line 443 C  UE4Editor-Sequencer-Win64-Debug.dll!FMovieSceneSequenceTransform::InverseFromWarp(const FMovieSceneWarpCounter & WarpCounter) Line 432 C  UE4Editor-Sequencer-Win64-Debug.dll!TMovieSceneTimeArray<FMovieSceneMarkedFrame>::UpdateCachedInverseTransform() Line 146 C  UE4Editor-Sequencer-Win64-Debug.dll!TMovieSceneTimeArray<FMovieSceneMarkedFrame>::PushTransform(const FMovieSceneTimeTransform & InTransform) Line 44 C  UE4Editor-Sequencer-Win64-Debug.dll!UE::MovieScene::FindGlobalMarkedFrames(const ISequencer & Sequencer, const FMovieSceneSequenceHierarchy * SequenceHierarchy, const FMovieSceneSequenceID & FocusedSequenceID, const FMovieSceneSequenceID & SequenceID, TRange<FFrameNumber> GatherRange, TMovieSceneTimeArray<FMovieSceneMarkedFrame> & OutTimestampedGlobalMarkedFrames) Line 76 C  UE4Editor-Sequencer-Win64-Debug.dll!UE::MovieScene::FindGlobalMarkedFrames(const ISequencer & Sequencer, const FMovieSceneSequenceHierarchy * SequenceHierarchy, const FMovieSceneSequenceID & FocusedSequenceID, const FMovieSceneSequenceID & SequenceID, TRange<FFrameNumber> GatherRange, TMovieSceneTimeArray<FMovieSceneMarkedFrame> & OutTimestampedGlobalMarkedFrames) Line 129 C  UE4Editor-Sequencer-Win64-Debug.dll!FSequencerMarkedFrameHelper::FindGlobalMarkedFrames(ISequencer & Sequencer, TArray<unsigned int,TSizedDefaultAllocator<32>> LoopCounter, TArray<FMovieSceneMarkedFrame,TSizedDefaultAllocator<32>> & OutGlobalMarkedFrames) Line 186 C  UE4Editor-Sequencer-Win64-Debug.dll!FSequencer::UpdateGlobalMarkedFramesCache() Line 11636 C  UE4Editor-Sequencer-Win64-Debug.dll!FSequencer::Tick(float InDeltaTime) Line 830 C  UE4Editor-UnrealEd-Win64-Debug.dll!FTickableEditorObject::TickObjects(const float DeltaSeconds) Line 45 C  UE4Editor-UnrealEd-Win64-Debug.dll!UEditorEngine::Tick(float DeltaSeconds, bool bIdleMode) Line 1502 C  UE4Editor-UnrealEd-Win64-Debug.dll!UUnrealEdEngine::Tick(float DeltaSeconds, bool bIdleMode) Line 426 C  UE4Editor-Win64-Debug.exe!FEngineLoop::Tick() Line 4922 C  UE4Editor-Win64-Debug.exe!EngineTick() Line 63 C  UE4Editor-Win64-Debug.exe!GuardedMain(const wchar_t * CmdLine) Line 181 C  UE4Editor-Win64-Debug.exe!LaunchWindowsStartup(HINSTANCE__ * hInInstance, HINSTANCE__ * hPrevInstance, char * _formal, int nCmdShow, const wchar_t * CmdLine) Line 262 C  UE4Editor-Win64-Debug.exe!WinMain(HINSTANCE_ * hInInstance, HINSTANCE__ * hPrevInstance, char * pCmdLine, int nCmdShow) Line 320 C+