wavparse: Don't do calculations with -1 offsets when handling SEGMENT events

We use that to signal "infinity", taking the difference between that and some
other value is not going to give us any useful result for the end offsets of
segments.

gst/wavparse/gstwavparse.c

@@ -2420,7 +2420,7 @@ gst_wavparse_sink_event (GstPad * pad, GstObject * parent, GstEvent * event)
       /* and set up streaming thread for next one */
       wav->offset = offset;
       wav->end_offset = end_offset;
-      if (wav->end_offset > 0) {
+      if (wav->end_offset != -1) {
         wav->dataleft = wav->end_offset - wav->offset;
       } else {
         /* infinity; upstream will EOS when done */