Since 1122a05cb6 tool settings could return None, but we do not check this
consistently in scripts. Now always return some tool settings, since it's difficult
to verify and easy to forget proper null checks in e.g. operator poll functions.
The sequencer UI code was updated to continue showing tool settings only when
there is a sequencer scene.
Co-authored-by: Sergey Sharybin <sergey@blender.org>
Pull Request: https://projects.blender.org/blender/blender/pulls/146166