avcodec/bitstream: assert that no integer overflow happened when writing codes in build_table()

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/bitstream.c

@@ -232,6 +232,7 @@ static int build_table(VLC *vlc, int table_nb_bits, int nb_codes,
             /* note: realloc has been done, so reload tables */
             table = &vlc->table[table_index];
             table[j][0] = index; //code
+            av_assert0(table[j][0] == index);
             i = k-1;
         }
     }