avcodec/bonk: Fix undefined overflow in predictor_calc_error()

Fixes: signed integer overflow: -2146469728 - 1488954 cannot be represented in type 'int'
Fixes: 62490/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_BONK_fuzzer-5612782399389696

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

libavcodec/bonk.c

@@ -270,7 +270,7 @@ static inline int shift(int a, int b)
 
 static int predictor_calc_error(int *k, int *state, int order, int error)
 {
-    int i, x = error - shift_down(k[order-1] * (unsigned)state[order-1], LATTICE_SHIFT);
+    int i, x = error - (unsigned)shift_down(k[order-1] * (unsigned)state[order-1], LATTICE_SHIFT);
     int *k_ptr = &(k[order-2]),
         *state_ptr = &(state[order-2]);