vqa: fix double free on corrupted streams

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

libavformat/westwood.c

@@ -277,10 +277,8 @@ static int wsvqa_read_header(AVFormatContext *s,
     /* there are 0 or more chunks before the FINF chunk; iterate until
      * FINF has been skipped and the file will be ready to be demuxed */
     do {
-        if (avio_read(pb, scratch, VQA_PREAMBLE_SIZE) != VQA_PREAMBLE_SIZE) {
-            av_free(st->codec->extradata);
+        if (avio_read(pb, scratch, VQA_PREAMBLE_SIZE) != VQA_PREAMBLE_SIZE)
             return AVERROR(EIO);
-        }
         chunk_tag = AV_RB32(&scratch[0]);
         chunk_size = AV_RB32(&scratch[4]);