ffmpeg.c:3531: error: Null Dereference
  pointer `p` last assigned on line 3531 could be null and is dereferenced at line 3531, column 5.

ffmpeg.c:3516:1: start of procedure opt_streamid()
3514. 
3515. /* arg format is "output-stream-index:streamid-value". */
3516. static int opt_streamid(const char *opt, const char *arg)
      ^
3517. {
3518.     int idx;

ffmpeg.c:3522:5: 
3520.     char idx_str[16];
3521. 
3522.     strncpy(idx_str, arg, sizeof(idx_str));
          ^
3523.     idx_str[sizeof(idx_str)-1] = '\0';
3524.     p = strchr(idx_str, ':');

ffmpeg.c:3523:5: 
3521. 
3522.     strncpy(idx_str, arg, sizeof(idx_str));
3523.     idx_str[sizeof(idx_str)-1] = '\0';
          ^
3524.     p = strchr(idx_str, ':');
3525.     if (!p) {

ffmpeg.c:3524:5: 
3522.     strncpy(idx_str, arg, sizeof(idx_str));
3523.     idx_str[sizeof(idx_str)-1] = '\0';
3524.     p = strchr(idx_str, ':');
          ^
3525.     if (!p) {
3526.         fprintf(stderr,

ffmpeg.c:3525:10: Taking true branch
3523.     idx_str[sizeof(idx_str)-1] = '\0';
3524.     p = strchr(idx_str, ':');
3525.     if (!p) {
               ^
3526.         fprintf(stderr,
3527.                 "Invalid value '%s' for option '%s', required syntax is 'index:value'\n",

ffmpeg.c:3526:9: 
3524.     p = strchr(idx_str, ':');
3525.     if (!p) {
3526.         fprintf(stderr,
              ^
3527.                 "Invalid value '%s' for option '%s', required syntax is 'index:value'\n",
3528.                 arg, opt);

ffmpeg.c:3529:9: Skipping ffmpeg_exit(): empty list of specs
3527.                 "Invalid value '%s' for option '%s', required syntax is 'index:value'\n",
3528.                 arg, opt);
3529.         ffmpeg_exit(1);
              ^
3530.     }
3531.     *p++ = '\0';

ffmpeg.c:3531:5: 
3529.         ffmpeg_exit(1);
3530.     }
3531.     *p++ = '\0';
          ^
3532.     idx = parse_number_or_die(opt, idx_str, OPT_INT, 0, MAX_STREAMS-1);
3533.     streamid_map = grow_array(streamid_map, sizeof(*streamid_map), &nb_streamid_map, idx+1);
