ffmpeg.c:3681: error: Null Dereference
  pointer `p` last assigned on line 3681 could be null and is dereferenced at line 3681, column 5.

ffmpeg.c:3666:1: start of procedure opt_streamid()
3664. 
3665. /* arg format is "output-stream-index:streamid-value". */
3666. static int opt_streamid(const char *opt, const char *arg)
      ^
3667. {
3668.     int idx;

ffmpeg.c:3672:5: 
3670.     char idx_str[16];
3671. 
3672.     strncpy(idx_str, arg, sizeof(idx_str));
          ^
3673.     idx_str[sizeof(idx_str)-1] = '\0';
3674.     p = strchr(idx_str, ':');

ffmpeg.c:3673:5: 
3671. 
3672.     strncpy(idx_str, arg, sizeof(idx_str));
3673.     idx_str[sizeof(idx_str)-1] = '\0';
          ^
3674.     p = strchr(idx_str, ':');
3675.     if (!p) {

ffmpeg.c:3674:5: 
3672.     strncpy(idx_str, arg, sizeof(idx_str));
3673.     idx_str[sizeof(idx_str)-1] = '\0';
3674.     p = strchr(idx_str, ':');
          ^
3675.     if (!p) {
3676.         fprintf(stderr,

ffmpeg.c:3675:10: Taking true branch
3673.     idx_str[sizeof(idx_str)-1] = '\0';
3674.     p = strchr(idx_str, ':');
3675.     if (!p) {
               ^
3676.         fprintf(stderr,
3677.                 "Invalid value '%s' for option '%s', required syntax is 'index:value'\n",

ffmpeg.c:3676:9: 
3674.     p = strchr(idx_str, ':');
3675.     if (!p) {
3676.         fprintf(stderr,
              ^
3677.                 "Invalid value '%s' for option '%s', required syntax is 'index:value'\n",
3678.                 arg, opt);

ffmpeg.c:3679:9: Skipping ffmpeg_exit(): empty list of specs
3677.                 "Invalid value '%s' for option '%s', required syntax is 'index:value'\n",
3678.                 arg, opt);
3679.         ffmpeg_exit(1);
              ^
3680.     }
3681.     *p++ = '\0';

ffmpeg.c:3681:5: 
3679.         ffmpeg_exit(1);
3680.     }
3681.     *p++ = '\0';
          ^
3682.     idx = parse_number_or_die(opt, idx_str, OPT_INT, 0, MAX_STREAMS-1);
3683.     streamid_map = grow_array(streamid_map, sizeof(*streamid_map), &nb_streamid_map, idx+1);
