avcodec/dirac_vlc: Fix invalid shift in ff_dirac_golomb_read_32bit()

Fixes: runtime error: shift exponent 64 is too large for 64-bit type 'residual' (aka 'unsigned long')
Fixes: 2838/clusterfuzz-testcase-minimized-6260066086813696

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 c595139f1f)
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/dirac_vlc.c

@@ -56,6 +56,9 @@ int ff_dirac_golomb_read_32bit(DiracGolombLUT *lut_ctx, const uint8_t *buf,
         if ((c_idx + 1) > coeffs)
             return c_idx;
 
+        if (res_bits >= RSIZE_BITS)
+            res_bits = res = 0;
+
         /* res_bits is a hint for better branch prediction */
         if (res_bits && l->sign) {
             int32_t coeff = 1;