ffmpeg.c:3684: error: Null Dereference
  pointer `p` last assigned on line 3684 could be null and is dereferenced at line 3684, column 5.

ffmpeg.c:3669:1: start of procedure opt_streamid()
3667. 
3668. /* arg format is "output-stream-index:streamid-value". */
3669. static int opt_streamid(const char *opt, const char *arg)
      ^
3670. {
3671.     int idx;

ffmpeg.c:3675:5: 
3673.     char idx_str[16];
3674. 
3675.     strncpy(idx_str, arg, sizeof(idx_str));
          ^
3676.     idx_str[sizeof(idx_str)-1] = '\0';
3677.     p = strchr(idx_str, ':');

ffmpeg.c:3676:5: 
3674. 
3675.     strncpy(idx_str, arg, sizeof(idx_str));
3676.     idx_str[sizeof(idx_str)-1] = '\0';
          ^
3677.     p = strchr(idx_str, ':');
3678.     if (!p) {

ffmpeg.c:3677:5: 
3675.     strncpy(idx_str, arg, sizeof(idx_str));
3676.     idx_str[sizeof(idx_str)-1] = '\0';
3677.     p = strchr(idx_str, ':');
          ^
3678.     if (!p) {
3679.         fprintf(stderr,

ffmpeg.c:3678:10: Taking true branch
3676.     idx_str[sizeof(idx_str)-1] = '\0';
3677.     p = strchr(idx_str, ':');
3678.     if (!p) {
               ^
3679.         fprintf(stderr,
3680.                 "Invalid value '%s' for option '%s', required syntax is 'index:value'\n",

ffmpeg.c:3679:9: 
3677.     p = strchr(idx_str, ':');
3678.     if (!p) {
3679.         fprintf(stderr,
              ^
3680.                 "Invalid value '%s' for option '%s', required syntax is 'index:value'\n",
3681.                 arg, opt);

ffmpeg.c:3682:9: Skipping ffmpeg_exit(): empty list of specs
3680.                 "Invalid value '%s' for option '%s', required syntax is 'index:value'\n",
3681.                 arg, opt);
3682.         ffmpeg_exit(1);
              ^
3683.     }
3684.     *p++ = '\0';

ffmpeg.c:3684:5: 
3682.         ffmpeg_exit(1);
3683.     }
3684.     *p++ = '\0';
          ^
3685.     idx = parse_number_or_die(opt, idx_str, OPT_INT, 0, MAX_STREAMS-1);
3686.     streamid_map = grow_array(streamid_map, sizeof(*streamid_map), &nb_streamid_map, idx+1);
