649cde421b
Do not try to kill thumbnail generation job when destroying the cache (which happens as part of destroying the scene) -- all the code paths that destroy a scene already cancel outstanding WM jobs. And WM itself might be gone at that point, so accessing a stale pointer to it can lead to a crash. Instead, fix the problem of "refresh sequencer can cause a crash" by not destroying the thumbnail cache, but merely clearing it in sequencer_refresh_all_exec. Pull Request: https://projects.blender.org/blender/blender/pulls/127485