vmdav: check that theres enough space for a chunk remaining.

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
(cherry picked from commit 2278ecc434)

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

libavcodec/vmdav.c

@@ -618,7 +618,7 @@ static int vmdaudio_decode_frame(AVCodecContext *avctx, void *data,
     /* decode audio chunks */
     if (audio_chunks > 0) {
         buf_end = buf + buf_size;
-        while (buf < buf_end) {
+        while ( buf_end - buf >= s->chunk_size) {
             if (s->out_bps == 2) {
                 decode_audio_s16(output_samples_s16, buf, s->chunk_size,
                                  avctx->channels);