The is_gst_mini_object_check would sometimes detect a proper GObject as a mini object, and then bad things happen. We know whether a pointer is a proper GObject or a MiniObject here though, so just pass that information to the right code paths and avoid the heuristics altogether. There are probably more cases where the check should be eliminated. Fixes #1334, maybe Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/2832>