gst/wavparse/gstwavparse.c: Ref the element when we should, but not when we its not needed. Reflow the event_handling...

Original commit message from CVS:
* gst/wavparse/gstwavparse.c: (gst_wavparse_stream_headers),
(gst_wavparse_pad_convert), (gst_wavparse_pad_query),
(gst_wavparse_srcpad_event):
Ref the element when we should, but not when we its not needed. Reflow
the event_handling to not leak the event.