avformat/aiffdec: sanity check block_align

Reviewed-by: Paul B Mahol <onemda@gmail.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavformat/aiffdec.c

@@ -368,7 +368,7 @@ got_sound:
     if (!st->codecpar->block_align && st->codecpar->codec_id == AV_CODEC_ID_QCELP) {
         av_log(s, AV_LOG_WARNING, "qcelp without wave chunk, assuming full rate\n");
         st->codecpar->block_align = 35;
-    } else if (!st->codecpar->block_align) {
+    } else if (st->codecpar->block_align <= 0) {
         av_log(s, AV_LOG_ERROR, "could not find COMM tag or invalid block_align value\n");
         return -1;
     }