avcodec/misc4: reject invalid sample rate

Fixes: AVERROR_BUG

Fixes: 493055111/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_MISC4_fuzzer-5752676962074624
Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/misc4.c

@@ -57,6 +57,9 @@ static av_cold int misc4_init(AVCodecContext *avctx)
 {
     MISC4Context *s = avctx->priv_data;
 
+    if (avctx->sample_rate <= 0)
+        return AVERROR_INVALIDDATA;
+
     avctx->sample_fmt = AV_SAMPLE_FMT_S16;
     switch (avctx->sample_rate) {
     case 8000: