The tree-type argument for the `supports_socket_type` type should be
allowed to be anything. There doesn't seem to be a great benefit in
restricting it. Always returning false when the tree type is not supported
makes sense.
In addition it would also be good to double-check that one can't add
the bundle and closure nodes in the compositor yet. From my basic tests,
that seems to work as expected.
f89b24ba8d