When a new workspace is appended into the current file, code tries to
set the active tool. As of #140271, an added check meant that if there
was no sequencer scene yet, no tool would be initialized with
`WM_toolsystem_update_from_context`.
In actuality, the scene and view layer that are passed into this
function are only used by the View3D space in
`WM_toolsystem_mode_from_spacetype`, so we don't need a special case at
all. Just revert to previous behavior to fix.
Pull Request: https://projects.blender.org/blender/blender/pulls/145860
b67d44fc70