tracker-extract-gstreamer: Don't test for NULL tagcache, it's never NULL
tracker-extract-gstreamer: Don't test for NULL tagcache, it's never NULL

Instead use !gst_tag_list_is_empty()

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