avcodec/vmdaudio: Check block_align more

Fixes: signed integer overflow: 2147483647 + 1 cannot be represented in type 'int'
Fixes: 19788/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_VMDAUDIO_fuzzer-5743379690553344

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Reviewed-by: Paul B Mahol <onemda@gmail.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/vmdaudio.c

@@ -76,7 +76,9 @@ static av_cold int vmdaudio_decode_init(AVCodecContext *avctx)
         av_log(avctx, AV_LOG_ERROR, "invalid number of channels\n");
         return AVERROR(EINVAL);
     }
-    if (avctx->block_align < 1 || avctx->block_align % avctx->channels) {
+    if (avctx->block_align < 1 || avctx->block_align % avctx->channels ||
+        avctx->block_align > INT_MAX - avctx->channels
+    ) {
         av_log(avctx, AV_LOG_ERROR, "invalid block align\n");
         return AVERROR(EINVAL);
     }