ffmpeg.c:3645: error: Null Dereference
  pointer `p` last assigned on line 3645 could be null and is dereferenced at line 3645, column 5.

ffmpeg.c:3630:1: start of procedure opt_streamid()
3628. 
3629. /* arg format is "output-stream-index:streamid-value". */
3630. static int opt_streamid(const char *opt, const char *arg)
      ^
3631. {
3632.     int idx;

ffmpeg.c:3636:5: 
3634.     char idx_str[16];
3635. 
3636.     strncpy(idx_str, arg, sizeof(idx_str));
          ^
3637.     idx_str[sizeof(idx_str)-1] = '\0';
3638.     p = strchr(idx_str, ':');

ffmpeg.c:3637:5: 
3635. 
3636.     strncpy(idx_str, arg, sizeof(idx_str));
3637.     idx_str[sizeof(idx_str)-1] = '\0';
          ^
3638.     p = strchr(idx_str, ':');
3639.     if (!p) {

ffmpeg.c:3638:5: 
3636.     strncpy(idx_str, arg, sizeof(idx_str));
3637.     idx_str[sizeof(idx_str)-1] = '\0';
3638.     p = strchr(idx_str, ':');
          ^
3639.     if (!p) {
3640.         fprintf(stderr,

ffmpeg.c:3639:10: Taking true branch
3637.     idx_str[sizeof(idx_str)-1] = '\0';
3638.     p = strchr(idx_str, ':');
3639.     if (!p) {
               ^
3640.         fprintf(stderr,
3641.                 "Invalid value '%s' for option '%s', required syntax is 'index:value'\n",

ffmpeg.c:3640:9: 
3638.     p = strchr(idx_str, ':');
3639.     if (!p) {
3640.         fprintf(stderr,
              ^
3641.                 "Invalid value '%s' for option '%s', required syntax is 'index:value'\n",
3642.                 arg, opt);

ffmpeg.c:3643:9: Skipping ffmpeg_exit(): empty list of specs
3641.                 "Invalid value '%s' for option '%s', required syntax is 'index:value'\n",
3642.                 arg, opt);
3643.         ffmpeg_exit(1);
              ^
3644.     }
3645.     *p++ = '\0';

ffmpeg.c:3645:5: 
3643.         ffmpeg_exit(1);
3644.     }
3645.     *p++ = '\0';
          ^
3646.     idx = parse_number_or_die(opt, idx_str, OPT_INT, 0, MAX_STREAMS-1);
3647.     streamid_map = grow_array(streamid_map, sizeof(*streamid_map), &nb_streamid_map, idx+1);
