Ctrl+Alt selection drag inside to outside of Matinee window will crash the editor
Reproduced in Releases stream 2982080 as well, to verify that this wasn't the same bug as https://jira.ol.epicgames.net/browse/UE-29265.
1. Open QA-game
2. Create Matinee Data > Place in the level
3. Go to the Details panel > Open Matinee
4. In the Tracks window, Ctrl-Alt Selection Drag from the center of the window to the outside (upwards seems to work about 100% of the time) and release the mouse-button
Results: The engine will crash when the selection window is released
Expected: For the selection window to be released and anything inside of the box to be selected and the engine to now crash
UE4Editor_Matinee!FMatineeViewportClient::InputKey() [matineeviewportclient.cpp:660] UE4Editor_Engine!FSceneViewport::OnMouseButtonUp() [sceneviewport.cpp:475] UE4Editor_Slate!SViewport::OnMouseButtonUp() [sviewport.cpp:187] UE4Editor_Slate!<lambda_9ed539f2a96fd1ccd6d2214174cc7705>::operator() [slateapplication.cpp:4540] UE4Editor_Slate!FEventRouter::Route<FReply,FEventRouter::FToLeafmostPolicy,FPointerEvent,<lambda_9ed539f2a96fd1ccd6d2214174cc7705> >() [slateapplication.cpp:214] UE4Editor_Slate!FSlateApplication::RoutePointerUpEvent() [slateapplication.cpp:4530] UE4Editor_Slate!FSlateApplication::ProcessMouseButtonUpEvent() [slateapplication.cpp:4947] UE4Editor_Slate!FSlateApplication::OnMouseUp() [slateapplication.cpp:4923] UE4Editor_Core!FWindowsApplication::ProcessDeferredMessage() [windowsapplication.cpp:1415] UE4Editor_Core!FWindowsApplication::DeferMessage() [windowsapplication.cpp:1732] UE4Editor_Core!FWindowsApplication::ProcessMessage() [windowsapplication.cpp:697] UE4Editor_Core!FWindowsApplication::AppWndProc() [windowsapplication.cpp:619] user32!<Unknown> user32!<Unknown> UE4Editor_Core!FWindowsPlatformMisc::PumpMessages() [windowsplatformmisc.cpp:884] UE4Editor!FEngineLoop::Tick() [launchengineloop.cpp:2611] UE4Editor!GuardedMain() [launch.cpp:142] UE4Editor!GuardedMainWrapper() [launchwindows.cpp:126] UE4Editor!WinMain() [launchwindows.cpp:200] UE4Editor!__scrt_common_main_seh() [exe_common.inl:264] kernel32!<Unknown> ntdll!<Unknown>
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