ffmpeg.c:3649: error: Null Dereference
  pointer `p` last assigned on line 3649 could be null and is dereferenced at line 3649, column 5.

ffmpeg.c:3634:1: start of procedure opt_streamid()
3632. 
3633. /* arg format is "output-stream-index:streamid-value". */
3634. static int opt_streamid(const char *opt, const char *arg)
      ^
3635. {
3636.     int idx;

ffmpeg.c:3640:5: 
3638.     char idx_str[16];
3639. 
3640.     strncpy(idx_str, arg, sizeof(idx_str));
          ^
3641.     idx_str[sizeof(idx_str)-1] = '\0';
3642.     p = strchr(idx_str, ':');

ffmpeg.c:3641:5: 
3639. 
3640.     strncpy(idx_str, arg, sizeof(idx_str));
3641.     idx_str[sizeof(idx_str)-1] = '\0';
          ^
3642.     p = strchr(idx_str, ':');
3643.     if (!p) {

ffmpeg.c:3642:5: 
3640.     strncpy(idx_str, arg, sizeof(idx_str));
3641.     idx_str[sizeof(idx_str)-1] = '\0';
3642.     p = strchr(idx_str, ':');
          ^
3643.     if (!p) {
3644.         fprintf(stderr,

ffmpeg.c:3643:10: Taking true branch
3641.     idx_str[sizeof(idx_str)-1] = '\0';
3642.     p = strchr(idx_str, ':');
3643.     if (!p) {
               ^
3644.         fprintf(stderr,
3645.                 "Invalid value '%s' for option '%s', required syntax is 'index:value'\n",

ffmpeg.c:3644:9: 
3642.     p = strchr(idx_str, ':');
3643.     if (!p) {
3644.         fprintf(stderr,
              ^
3645.                 "Invalid value '%s' for option '%s', required syntax is 'index:value'\n",
3646.                 arg, opt);

ffmpeg.c:3647:9: Skipping ffmpeg_exit(): empty list of specs
3645.                 "Invalid value '%s' for option '%s', required syntax is 'index:value'\n",
3646.                 arg, opt);
3647.         ffmpeg_exit(1);
              ^
3648.     }
3649.     *p++ = '\0';

ffmpeg.c:3649:5: 
3647.         ffmpeg_exit(1);
3648.     }
3649.     *p++ = '\0';
          ^
3650.     idx = parse_number_or_die(opt, idx_str, OPT_INT, 0, MAX_STREAMS-1);
3651.     streamid_map = grow_array(streamid_map, sizeof(*streamid_map), &nb_streamid_map, idx+1);
