ffmpeg.c:3683: error: Null Dereference
  pointer `p` last assigned on line 3683 could be null and is dereferenced at line 3683, column 5.

ffmpeg.c:3668:1: start of procedure opt_streamid()
3666. 
3667. /* arg format is "output-stream-index:streamid-value". */
3668. static int opt_streamid(const char *opt, const char *arg)
      ^
3669. {
3670.     int idx;

ffmpeg.c:3674:5: 
3672.     char idx_str[16];
3673. 
3674.     strncpy(idx_str, arg, sizeof(idx_str));
          ^
3675.     idx_str[sizeof(idx_str)-1] = '\0';
3676.     p = strchr(idx_str, ':');

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

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

ffmpeg.c:3677:10: Taking true branch
3675.     idx_str[sizeof(idx_str)-1] = '\0';
3676.     p = strchr(idx_str, ':');
3677.     if (!p) {
               ^
3678.         fprintf(stderr,
3679.                 "Invalid value '%s' for option '%s', required syntax is 'index:value'\n",

ffmpeg.c:3678:9: 
3676.     p = strchr(idx_str, ':');
3677.     if (!p) {
3678.         fprintf(stderr,
              ^
3679.                 "Invalid value '%s' for option '%s', required syntax is 'index:value'\n",
3680.                 arg, opt);

ffmpeg.c:3681:9: Skipping ffmpeg_exit(): empty list of specs
3679.                 "Invalid value '%s' for option '%s', required syntax is 'index:value'\n",
3680.                 arg, opt);
3681.         ffmpeg_exit(1);
              ^
3682.     }
3683.     *p++ = '\0';

ffmpeg.c:3683:5: 
3681.         ffmpeg_exit(1);
3682.     }
3683.     *p++ = '\0';
          ^
3684.     idx = parse_number_or_die(opt, idx_str, OPT_INT, 0, MAX_STREAMS-1);
3685.     streamid_map = grow_array(streamid_map, sizeof(*streamid_map), &nb_streamid_map, idx+1);
