avcodec/apedec: Fix undefined integer overflow with 24bit

Fixes: signed integer overflow: 8683744 * 256 cannot be represented in type 'int'
Fixes: 23527/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_APE_fuzzer-5679885932822528

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

libavcodec/apedec.c

@@ -1569,7 +1569,7 @@ static int ape_decode_frame(AVCodecContext *avctx, void *data,
         for (ch = 0; ch < s->channels; ch++) {
             sample24 = (int32_t *)frame->data[ch];
             for (i = 0; i < blockstodecode; i++)
-                *sample24++ = s->decoded[ch][i] * 256;
+                *sample24++ = s->decoded[ch][i] * 256U;
         }
         break;
     }