ffmpeg.c:3584: error: Null Dereference
  pointer `p` last assigned on line 3584 could be null and is dereferenced at line 3584, column 5.

ffmpeg.c:3569:1: start of procedure opt_streamid()
3567. 
3568. /* arg format is "output-stream-index:streamid-value". */
3569. static int opt_streamid(const char *opt, const char *arg)
      ^
3570. {
3571.     int idx;

ffmpeg.c:3575:5: 
3573.     char idx_str[16];
3574. 
3575.     strncpy(idx_str, arg, sizeof(idx_str));
          ^
3576.     idx_str[sizeof(idx_str)-1] = '\0';
3577.     p = strchr(idx_str, ':');

ffmpeg.c:3576:5: 
3574. 
3575.     strncpy(idx_str, arg, sizeof(idx_str));
3576.     idx_str[sizeof(idx_str)-1] = '\0';
          ^
3577.     p = strchr(idx_str, ':');
3578.     if (!p) {

ffmpeg.c:3577:5: 
3575.     strncpy(idx_str, arg, sizeof(idx_str));
3576.     idx_str[sizeof(idx_str)-1] = '\0';
3577.     p = strchr(idx_str, ':');
          ^
3578.     if (!p) {
3579.         fprintf(stderr,

ffmpeg.c:3578:10: Taking true branch
3576.     idx_str[sizeof(idx_str)-1] = '\0';
3577.     p = strchr(idx_str, ':');
3578.     if (!p) {
               ^
3579.         fprintf(stderr,
3580.                 "Invalid value '%s' for option '%s', required syntax is 'index:value'\n",

ffmpeg.c:3579:9: 
3577.     p = strchr(idx_str, ':');
3578.     if (!p) {
3579.         fprintf(stderr,
              ^
3580.                 "Invalid value '%s' for option '%s', required syntax is 'index:value'\n",
3581.                 arg, opt);

ffmpeg.c:3582:9: Skipping ffmpeg_exit(): empty list of specs
3580.                 "Invalid value '%s' for option '%s', required syntax is 'index:value'\n",
3581.                 arg, opt);
3582.         ffmpeg_exit(1);
              ^
3583.     }
3584.     *p++ = '\0';

ffmpeg.c:3584:5: 
3582.         ffmpeg_exit(1);
3583.     }
3584.     *p++ = '\0';
          ^
3585.     idx = parse_number_or_die(opt, idx_str, OPT_INT, 0, MAX_STREAMS-1);
3586.     streamid_map = grow_array(streamid_map, sizeof(*streamid_map), &nb_streamid_map, idx+1);
