ffmpeg.c:3664: error: Null Dereference
  pointer `p` last assigned on line 3664 could be null and is dereferenced at line 3664, column 5.

ffmpeg.c:3649:1: start of procedure opt_streamid()
3647. 
3648. /* arg format is "output-stream-index:streamid-value". */
3649. static int opt_streamid(const char *opt, const char *arg)
      ^
3650. {
3651.     int idx;

ffmpeg.c:3655:5: 
3653.     char idx_str[16];
3654. 
3655.     strncpy(idx_str, arg, sizeof(idx_str));
          ^
3656.     idx_str[sizeof(idx_str)-1] = '\0';
3657.     p = strchr(idx_str, ':');

ffmpeg.c:3656:5: 
3654. 
3655.     strncpy(idx_str, arg, sizeof(idx_str));
3656.     idx_str[sizeof(idx_str)-1] = '\0';
          ^
3657.     p = strchr(idx_str, ':');
3658.     if (!p) {

ffmpeg.c:3657:5: 
3655.     strncpy(idx_str, arg, sizeof(idx_str));
3656.     idx_str[sizeof(idx_str)-1] = '\0';
3657.     p = strchr(idx_str, ':');
          ^
3658.     if (!p) {
3659.         fprintf(stderr,

ffmpeg.c:3658:10: Taking true branch
3656.     idx_str[sizeof(idx_str)-1] = '\0';
3657.     p = strchr(idx_str, ':');
3658.     if (!p) {
               ^
3659.         fprintf(stderr,
3660.                 "Invalid value '%s' for option '%s', required syntax is 'index:value'\n",

ffmpeg.c:3659:9: 
3657.     p = strchr(idx_str, ':');
3658.     if (!p) {
3659.         fprintf(stderr,
              ^
3660.                 "Invalid value '%s' for option '%s', required syntax is 'index:value'\n",
3661.                 arg, opt);

ffmpeg.c:3662:9: Skipping ffmpeg_exit(): empty list of specs
3660.                 "Invalid value '%s' for option '%s', required syntax is 'index:value'\n",
3661.                 arg, opt);
3662.         ffmpeg_exit(1);
              ^
3663.     }
3664.     *p++ = '\0';

ffmpeg.c:3664:5: 
3662.         ffmpeg_exit(1);
3663.     }
3664.     *p++ = '\0';
          ^
3665.     idx = parse_number_or_die(opt, idx_str, OPT_INT, 0, MAX_STREAMS-1);
3666.     streamid_map = grow_array(streamid_map, sizeof(*streamid_map), &nb_streamid_map, idx+1);
