ffmpeg.c:3688: error: Null Dereference
  pointer `p` last assigned on line 3688 could be null and is dereferenced at line 3688, column 5.

ffmpeg.c:3673:1: start of procedure opt_streamid()
3671. 
3672. /* arg format is "output-stream-index:streamid-value". */
3673. static void opt_streamid(const char *opt, const char *arg)
      ^
3674. {
3675.     int idx;

ffmpeg.c:3679:5: 
3677.     char idx_str[16];
3678. 
3679.     strncpy(idx_str, arg, sizeof(idx_str));
          ^
3680.     idx_str[sizeof(idx_str)-1] = '\0';
3681.     p = strchr(idx_str, ':');

ffmpeg.c:3680:5: 
3678. 
3679.     strncpy(idx_str, arg, sizeof(idx_str));
3680.     idx_str[sizeof(idx_str)-1] = '\0';
          ^
3681.     p = strchr(idx_str, ':');
3682.     if (!p) {

ffmpeg.c:3681:5: 
3679.     strncpy(idx_str, arg, sizeof(idx_str));
3680.     idx_str[sizeof(idx_str)-1] = '\0';
3681.     p = strchr(idx_str, ':');
          ^
3682.     if (!p) {
3683.         fprintf(stderr,

ffmpeg.c:3682:10: Taking true branch
3680.     idx_str[sizeof(idx_str)-1] = '\0';
3681.     p = strchr(idx_str, ':');
3682.     if (!p) {
               ^
3683.         fprintf(stderr,
3684.                 "Invalid value '%s' for option '%s', required syntax is 'index:value'\n",

ffmpeg.c:3683:9: 
3681.     p = strchr(idx_str, ':');
3682.     if (!p) {
3683.         fprintf(stderr,
              ^
3684.                 "Invalid value '%s' for option '%s', required syntax is 'index:value'\n",
3685.                 arg, opt);

ffmpeg.c:3686:9: Skipping ffmpeg_exit(): empty list of specs
3684.                 "Invalid value '%s' for option '%s', required syntax is 'index:value'\n",
3685.                 arg, opt);
3686.         ffmpeg_exit(1);
              ^
3687.     }
3688.     *p++ = '\0';

ffmpeg.c:3688:5: 
3686.         ffmpeg_exit(1);
3687.     }
3688.     *p++ = '\0';
          ^
3689.     idx = parse_number_or_die(opt, idx_str, OPT_INT, 0, MAX_STREAMS-1);
3690.     streamid_map = grow_array(streamid_map, sizeof(*streamid_map), &nb_streamid_map, idx+1);
