This commit introduces the following changes:
* Modified the poll callback on the "Update Paths" operator for bones
so that it only checks if there are bones that have motion paths
(instead of checking whether the active bone has paths).
This makes it easier to update paths without having to first select one
that has them - useful when the paths are all on hidden/hard-to-select bones.
* Add a readonly property, "has_motion_paths" to the animviz.motion_path
RNA struct, providing easier access to the internal flag used above.
This makes it possible for the UI to display the "Update" button without
having to check various bones for motion paths.
Notes:
* The flag being used in these changes already existed, and was only really
intended for internal use. However, since it was already used in many places
for determining if auto-update of all bone paths was needed (e.g. after certain
editing ops), it should be safe to use here too.
* The update_paths operator currently bakes all paths when activated, so there's
currently no loss of functionality with changing to not checking if the active
bone has any paths (e.g. we couldn't only update the active bone only either).
That is still listed as a todo in the code.
c5f59f5854