Unreal Engine Issues and Bug Tracker (UE-46206)

Description

Encountered an Access Violation crash while deleting an Widget Blueprint with an unsaved Animation Track.
The callstack references FSequencer::Tick().

I was not able to reproduce this issue in UE4/Main at CL 3496309.
It is therefore marked as a Regression.

Steps to Reproduce

Create and open a Widget Blueprint
Add a Button to the Designer
Add an Animation track to the Widget BP
Add the button to the Animation track
Add a Transform Track to the Animation track
Close the Widget BP. DO NOT SAVE OR COMPILE
Delete the Widget BP

Result:
Editor crashes with an Access Violation error referencing FSquencer::Tick()

Expected Result:
The Widget BP is deleted without errors or warnings

Frequency:
7/7

Callstack

[2017.06.19-15.53.29:762][415]LogWindows: Error: === Critical error: ===
[2017.06.19-15.53.29:762][415]LogWindows: Error: 
[2017.06.19-15.53.29:762][415]LogWindows: Error: Fatal error!
[2017.06.19-15.53.29:762][415]LogWindows: Error: 
[2017.06.19-15.53.29:762][415]LogWindows: Error: Unhandled Exception: EXCEPTION_ACCESS_VIOLATION reading address 0x00000000
[2017.06.19-15.53.29:762][415]LogWindows: Error: 
[2017.06.19-15.53.29:762][415]LogWindows: Error: UE4Editor-Sequencer.dll!FSequencer::Tick() [d:\engine\dev-editor\engine\source\editor\sequencer\private\sequencer.cpp:438]
[2017.06.19-15.53.29:762][415]LogWindows: Error: UE4Editor-UnrealEd.dll!FTickableEditorObject::TickObjects() [d:\engine\dev-editor\engine\source\editor\unrealed\public\tickableeditorobject.h:21]
[2017.06.19-15.53.29:762][415]LogWindows: Error: UE4Editor-UnrealEd.dll!UEditorEngine::Tick() [d:\engine\dev-editor\engine\source\editor\unrealed\private\editorengine.cpp:1414]
[2017.06.19-15.53.29:763][415]LogWindows: Error: UE4Editor-UnrealEd.dll!UUnrealEdEngine::Tick() [d:\engine\dev-editor\engine\source\editor\unrealed\private\unrealedengine.cpp:392]
[2017.06.19-15.53.29:763][415]LogWindows: Error: UE4Editor.exe!FEngineLoop::Tick() [d:\engine\dev-editor\engine\source\runtime\launch\private\launchengineloop.cpp:3191]
[2017.06.19-15.53.29:763][415]LogWindows: Error: UE4Editor.exe!GuardedMain() [d:\engine\dev-editor\engine\source\runtime\launch\private\launch.cpp:166]
[2017.06.19-15.53.29:763][415]LogWindows: Error: UE4Editor.exe!GuardedMainWrapper() [d:\engine\dev-editor\engine\source\runtime\launch\private\windows\launchwindows.cpp:134]
[2017.06.19-15.53.29:763][415]LogWindows: Error: UE4Editor.exe!WinMain() [d:\engine\dev-editor\engine\source\runtime\launch\private\windows\launchwindows.cpp:210]
[2017.06.19-15.53.29:763][415]LogWindows: Error: UE4Editor.exe!__scrt_common_main_seh() [f:\dd\vctools\crt\vcstartup\src\startup\exe_common.inl:253]
[2017.06.19-15.53.29:763][415]LogWindows: Error: kernel32.dll!0x00000000775F59CD
[2017.06.19-15.53.29:764][415]LogWindows: Error: ntdll.dll!0x000000007772A561
[2017.06.19-15.53.29:764][415]LogWindows: Error: ntdll.dll!0x000000007772A561
[2017.06.19-15.53.29:764][415]LogWindows: Error: 
[2017.06.19-15.53.29:774][415]LogExit: Executing StaticShutdownAfterError
[2017.06.19-15.53.29:777][415]LogWindows: FPlatformMisc::RequestExit(1)
[2017.06.19-15.53.29:777][415]Log file closed, 06/19/17 11:53:29

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Fixed

Component	UE - Anim - Sequencer
Affects Versions	4.17
Target Fix	4.17

Fix Commit	3500478
Main Commit	3500478

Created	Jun 19, 2017
Resolved	Jun 20, 2017
Updated	Apr 27, 2018

UE-46206

Access Violation crash deleting a Widget Blueprint with an unsaved Animation track - FSequencer::Tick()

Access Violation crash deleting a Widget Blueprint with an unsaved Animation track - FSequencer::Tick()

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