Change the `Action.id_root` RNA definition such that
`Action.bl_rna.properties["id_root"].enum_items` returns all valid
values for that property. This was the Blender 4.2 (and older) behaviour
as well.
The only difference now is that v4.3 adds a new `UNSPECIFIED` enum item,
which is not a valid ID type, but is a valid value for `Action.id_root`.
Some more context:
In Blender 4.2 the `Action.id_root` property was a hard-coded list of
all ID types. To add the `UNSPECIFIED` item in v4.3, this was replaced
by an 'items' callback. The way Blender deals with this by default is
such that querying `Action.bl_rna.properties["id_root"].enum_items`
returns its hard-coded default list, and not the result of that 'items'
callback function.
For Action Slots (which will be released in v4.4 but are already in the
sources as experimental feature), there is a similar property that is
implemented in a way such that its `.enum_items` always returns the
proper list. This commit updates the `Action.id_root` RNA property
definition so that it shares code with `ActionSlot.id_root`, fixing the
reported issue.
Note that the `ActionSlot` type is not exposed to RNA in Blender 4.3,
it's just some internal code that is now shared.
Pull Request: https://projects.blender.org/blender/blender/pulls/128834
d261a881b1