ffmpeg.c:3648: error: Null Dereference
  pointer `p` last assigned on line 3648 could be null and is dereferenced at line 3648, column 5.

ffmpeg.c:3633:1: start of procedure opt_streamid()
3631. 
3632. /* arg format is "output-stream-index:streamid-value". */
3633. static int opt_streamid(const char *opt, const char *arg)
      ^
3634. {
3635.     int idx;

ffmpeg.c:3639:5: 
3637.     char idx_str[16];
3638. 
3639.     strncpy(idx_str, arg, sizeof(idx_str));
          ^
3640.     idx_str[sizeof(idx_str)-1] = '\0';
3641.     p = strchr(idx_str, ':');

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

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

ffmpeg.c:3642:10: Taking true branch
3640.     idx_str[sizeof(idx_str)-1] = '\0';
3641.     p = strchr(idx_str, ':');
3642.     if (!p) {
               ^
3643.         fprintf(stderr,
3644.                 "Invalid value '%s' for option '%s', required syntax is 'index:value'\n",

ffmpeg.c:3643:9: 
3641.     p = strchr(idx_str, ':');
3642.     if (!p) {
3643.         fprintf(stderr,
              ^
3644.                 "Invalid value '%s' for option '%s', required syntax is 'index:value'\n",
3645.                 arg, opt);

ffmpeg.c:3646:9: Skipping ffmpeg_exit(): empty list of specs
3644.                 "Invalid value '%s' for option '%s', required syntax is 'index:value'\n",
3645.                 arg, opt);
3646.         ffmpeg_exit(1);
              ^
3647.     }
3648.     *p++ = '\0';

ffmpeg.c:3648:5: 
3646.         ffmpeg_exit(1);
3647.     }
3648.     *p++ = '\0';
          ^
3649.     idx = parse_number_or_die(opt, idx_str, OPT_INT, 0, MAX_STREAMS-1);
3650.     streamid_map = grow_array(streamid_map, sizeof(*streamid_map), &nb_streamid_map, idx+1);
