Blender Git Loki

Cleanup: animation, reduce complexity of RNA update function

Reduce complexity of `rna_SpaceDopeSheetEditor_action_update()` by flipping
conditions and returning early.

The depsgraph tagging has slightly changed, in that the depsgraph is not
tagged at all when there is no actual animation data added. I still see
this as a non-functional change, though, as in that case nothing changed
and tagging and re-evaluating wouldn't make any actual difference.

No functional changes.