ffmpeg.c:3679: error: Null Dereference
  pointer `p` last assigned on line 3679 could be null and is dereferenced at line 3679, column 5.

ffmpeg.c:3664:1: start of procedure opt_streamid()
3662. 
3663. /* arg format is "output-stream-index:streamid-value". */
3664. static int opt_streamid(const char *opt, const char *arg)
      ^
3665. {
3666.     int idx;

ffmpeg.c:3670:5: 
3668.     char idx_str[16];
3669. 
3670.     strncpy(idx_str, arg, sizeof(idx_str));
          ^
3671.     idx_str[sizeof(idx_str)-1] = '\0';
3672.     p = strchr(idx_str, ':');

ffmpeg.c:3671:5: 
3669. 
3670.     strncpy(idx_str, arg, sizeof(idx_str));
3671.     idx_str[sizeof(idx_str)-1] = '\0';
          ^
3672.     p = strchr(idx_str, ':');
3673.     if (!p) {

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

ffmpeg.c:3673:10: Taking true branch
3671.     idx_str[sizeof(idx_str)-1] = '\0';
3672.     p = strchr(idx_str, ':');
3673.     if (!p) {
               ^
3674.         fprintf(stderr,
3675.                 "Invalid value '%s' for option '%s', required syntax is 'index:value'\n",

ffmpeg.c:3674:9: 
3672.     p = strchr(idx_str, ':');
3673.     if (!p) {
3674.         fprintf(stderr,
              ^
3675.                 "Invalid value '%s' for option '%s', required syntax is 'index:value'\n",
3676.                 arg, opt);

ffmpeg.c:3677:9: Skipping ffmpeg_exit(): empty list of specs
3675.                 "Invalid value '%s' for option '%s', required syntax is 'index:value'\n",
3676.                 arg, opt);
3677.         ffmpeg_exit(1);
              ^
3678.     }
3679.     *p++ = '\0';

ffmpeg.c:3679:5: 
3677.         ffmpeg_exit(1);
3678.     }
3679.     *p++ = '\0';
          ^
3680.     idx = parse_number_or_die(opt, idx_str, OPT_INT, 0, MAX_STREAMS-1);
3681.     streamid_map = grow_array(streamid_map, sizeof(*streamid_map), &nb_streamid_map, idx+1);
