avcodec/sonic: Use unsigned for predictor_k to avoid undefined behavior

Fixes: signed integer overflow: -1094995529 * 24 cannot be represented in type 'int'
Fixes: 44436/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_SONIC_fuzzer-4874459459223552

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

libavcodec/sonic.c

@@ -1009,7 +1009,7 @@ static int sonic_decode_frame(AVCodecContext *avctx,
 
     // dequantize
     for (i = 0; i < s->num_taps; i++)
-        s->predictor_k[i] *= s->tap_quant[i];
+        s->predictor_k[i] *= (unsigned) s->tap_quant[i];
 
     if (s->lossless)
         quant = 1;