Since the introduction of the sequencer scene, some of the sequencer python operators have been using `context.scene` when they should be using `context.workspace.sequencer_scene`. This fixes `SequencerFadesAdd`, `SequencerFadesClear`, `SequencerDeinterlaceSelectedMovies`, `SequencerSplitMulticam`, and `SequencerCrossfadeSounds`. Pull Request: https://projects.blender.org/blender/blender/pulls/147560