avcodec/apedec: Fix undefined integer overflow in long_filter_ehigh_3830()

Fixes: signed integer overflow: -2145648640 - 3357696 cannot be represented in type 'int'
Fixes: 38899/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_APE_fuzzer-5358815017566208

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

@@ -979,7 +979,7 @@ static void long_filter_ehigh_3830(int32_t *buffer, int length)
         for (j = 7; j > 0; j--)
             delay[j] = delay[j - 1];
         delay[0] = buffer[i];
-        buffer[i] -= dotprod >> 9;
+        buffer[i] -= (unsigned)(dotprod >> 9);
     }
 }