avcodec/h264_cabac: runtime error: signed integer overflow: 2147483647 + 14 cannot be represented in type 'int'

Fixes: 614/clusterfuzz-testcase-4931860079575040

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

libavcodec/h264_cabac.c

@@ -1743,7 +1743,7 @@ decode_cabac_residual_internal(const H264Context *h, H264SliceContext *sl,
                 while( j-- ) { \
                     coeff_abs += coeff_abs + get_cabac_bypass( CC ); \
                 } \
-                coeff_abs+= 14; \
+                coeff_abs+= 14U; \
             } \
 \
             if( is_dc ) { \