gst/id3demux/id3v2frames.c: Don't output any tag when we encounter a negative track number - the tag type is uint, so...

Original commit message from CVS:
* gst/id3demux/id3v2frames.c: (id3v2_tag_to_taglist):
Don't output any tag when we encounter a negative track number - the
tag type is uint, so we end up outputting huge positive numbers
instead. (Fixes: #342029)