wtvdec: fix a few memleaks as show by valgrind with the FATE test.

Signed-off-by: Reimar Döffinger <Reimar.Doeffinger@gmx.de>

libavformat/wtvdec.c

@@ -287,6 +287,8 @@ static void wtvfile_close(AVIOContext *pb)
 {
     WtvFile *wf = pb->opaque;
     av_free(wf->sectors);
+    av_freep(&pb->opaque);
+    av_freep(&pb->buffer);
     av_free(pb);
 }