avformat/nuv: Check channels

Fixes: signed integer overflow: -3468545475927866368 * 4 cannot be represented in type 'long'
Fixes: 28879/clusterfuzz-testcase-minimized-ffmpeg_dem_NUV_fuzzer-6303367307591680

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

libavformat/nuv.c

@@ -117,6 +117,10 @@ static int get_codec_data(AVFormatContext *s, AVIOContext *pb, AVStream *vst,
                 ast->codecpar->bits_per_coded_sample = avio_rl32(pb);
                 ast->codecpar->channels              = avio_rl32(pb);
                 ast->codecpar->channel_layout        = 0;
+                if (ast->codecpar->channels <= 0) {
+                    av_log(s, AV_LOG_ERROR, "Invalid channels %d\n", ast->codecpar->channels);
+                    return AVERROR_INVALIDDATA;
+                }
 
                 id = ff_wav_codec_get_id(ast->codecpar->codec_tag,
                                          ast->codecpar->bits_per_coded_sample);