fix warning: assignment makes pointer from integer without a cast

Originally committed as revision 16523 to svn://svn.ffmpeg.org/ffmpeg/trunk

ffplay.c

@@ -2071,7 +2071,7 @@ static int decode_thread(void *arg)
         }
         if(url_feof(ic->pb)) {
             av_init_packet(pkt);
-            pkt->data=
+            pkt->data=NULL;
             pkt->size=0;
             pkt->stream_index= is->video_stream;
             packet_queue_put(&is->videoq, pkt);