tracker-extract: Fixes for the GStreamer extractor
tracker-extract: Fixes for the GStreamer extractor

This patch avoids a critical in case of a bug in tagreadbin
NB #158636. I also added the rdf:type in case there's no tag cache.

hoheinzollern/tracker,outofbits/tracker,hoheinzollern/tracker,outofbits/tracker,hoheinzollern/tracker,hoheinzollern/tracker,outofbits/tracker,outofbits/tracker,hoheinzollern/tracker,hoheinzollern/tracker,hoheinzollern/tracker,outofbits/tracker,outofbits/tracker,outofbits/tracker