avformat/sapenc: Use avio_closep() to avoid leaving stale pointers in memory

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavformat/sapenc.c

@@ -49,7 +49,7 @@ static int sap_write_close(AVFormatContext *s)
         if (!rtpctx)
             continue;
         av_write_trailer(rtpctx);
-        avio_close(rtpctx->pb);
+        avio_closep(&rtpctx->pb);
         avformat_free_context(rtpctx);
         s->streams[i]->priv_data = NULL;
     }