avcodec/apedec: fix integer overflow in 8bit samples

Fixes: signed integer overflow: 2147483542 + 128 cannot be represented in type 'int'
Fixes: 42812/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_APE_fuzzer-6344057861832704

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg


Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
(cherry picked from commit 7cee3b37)
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/apedec.c

@@ -1521,7 +1521,7 @@ static int ape_decode_frame(AVCodecContext *avctx, void *data,
         for (ch = 0; ch < s->channels; ch++) {
             sample8 = (uint8_t *)frame->data[ch];
             for (i = 0; i < blockstodecode; i++)
-                *sample8++ = (s->decoded[ch][i] + 0x80) & 0xff;
+                *sample8++ = (s->decoded[ch][i] + 0x80U) & 0xff;
         }
         break;
     case 16: