urisourcebin: Reference counting leak

When upgrading to GStreamer 1.24.9 we noticed that there is a GstStreamCollection leak in urisourcebin. The leak was introduced here: !7764 (diffs) The problem is that the reference count of the GstStreamCollection is increased twice. First by the call to gst_object_replace two lines up in the linked MR and then again in the line linked. Changing from "return res ? gst_object_ref (res) : NULL;" to just "return res;" solves the problem.

This leak is still present in GStreamer 1.24.10. I have not tested with the latest code from git main.