ffmpeg.c:3689: error: Null Dereference
  pointer `p` last assigned on line 3689 could be null and is dereferenced at line 3689, column 5.

ffmpeg.c:3674:1: start of procedure opt_streamid()
3672. 
3673. /* arg format is "output-stream-index:streamid-value". */
3674. static int opt_streamid(const char *opt, const char *arg)
      ^
3675. {
3676.     int idx;

ffmpeg.c:3680:5: 
3678.     char idx_str[16];
3679. 
3680.     strncpy(idx_str, arg, sizeof(idx_str));
          ^
3681.     idx_str[sizeof(idx_str)-1] = '\0';
3682.     p = strchr(idx_str, ':');

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

ffmpeg.c:3682:5: 
3680.     strncpy(idx_str, arg, sizeof(idx_str));
3681.     idx_str[sizeof(idx_str)-1] = '\0';
3682.     p = strchr(idx_str, ':');
          ^
3683.     if (!p) {
3684.         fprintf(stderr,

ffmpeg.c:3683:10: Taking true branch
3681.     idx_str[sizeof(idx_str)-1] = '\0';
3682.     p = strchr(idx_str, ':');
3683.     if (!p) {
               ^
3684.         fprintf(stderr,
3685.                 "Invalid value '%s' for option '%s', required syntax is 'index:value'\n",

ffmpeg.c:3684:9: 
3682.     p = strchr(idx_str, ':');
3683.     if (!p) {
3684.         fprintf(stderr,
              ^
3685.                 "Invalid value '%s' for option '%s', required syntax is 'index:value'\n",
3686.                 arg, opt);

ffmpeg.c:3687:9: Skipping ffmpeg_exit(): empty list of specs
3685.                 "Invalid value '%s' for option '%s', required syntax is 'index:value'\n",
3686.                 arg, opt);
3687.         ffmpeg_exit(1);
              ^
3688.     }
3689.     *p++ = '\0';

ffmpeg.c:3689:5: 
3687.         ffmpeg_exit(1);
3688.     }
3689.     *p++ = '\0';
          ^
3690.     idx = parse_number_or_die(opt, idx_str, OPT_INT, 0, MAX_STREAMS-1);
3691.     streamid_map = grow_array(streamid_map, sizeof(*streamid_map), &nb_streamid_map, idx+1);
