avcodec/bonk: Avoid undefined integer overflow in predictor_calc_error()

Fixes: signed integer overflow: -159584 * 5105950 cannot be represented in type 'int'
Fixes: 55165/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_BONK_fuzzer-5796023719297024

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 43e5e2e423)
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/bonk.c

@@ -270,14 +270,14 @@ 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] * state[order-1], LATTICE_SHIFT);
+    int i, x = error - shift_down(k[order-1] * (unsigned)state[order-1], LATTICE_SHIFT);
     int *k_ptr = &(k[order-2]),
         *state_ptr = &(state[order-2]);
 
     for (i = order-2; i >= 0; i--, k_ptr--, state_ptr--) {
         unsigned k_value = *k_ptr, state_value = *state_ptr;
 
-        x -= shift_down(k_value * state_value, LATTICE_SHIFT);
+        x -= shift_down(k_value * (unsigned)state_value, LATTICE_SHIFT);
         state_ptr[1] = state_value + shift_down(k_value * x, LATTICE_SHIFT);
     }