ffmpeg.c:2621: error: Null Dereference
  pointer `mid` last assigned on line 2621 could be null and is dereferenced at line 2621, column 5.

ffmpeg.c:2613:1: start of procedure opt_metadata()
2611. }
2612. 
2613. static int opt_metadata(const char *opt, const char *arg)
      ^
2614. {
2615.     char *mid= strchr(arg, '=');

ffmpeg.c:2615:5: 
2613. static int opt_metadata(const char *opt, const char *arg)
2614. {
2615.     char *mid= strchr(arg, '=');
          ^
2616. 
2617.     if(!mid){

ffmpeg.c:2617:9: Taking true branch
2615.     char *mid= strchr(arg, '=');
2616. 
2617.     if(!mid){
              ^
2618.         fprintf(stderr, "Missing =\n");
2619.         av_exit(1);

ffmpeg.c:2618:9: 
2616. 
2617.     if(!mid){
2618.         fprintf(stderr, "Missing =\n");
              ^
2619.         av_exit(1);
2620.     }

ffmpeg.c:2619:9: Skipping av_exit(): empty list of specs
2617.     if(!mid){
2618.         fprintf(stderr, "Missing =\n");
2619.         av_exit(1);
              ^
2620.     }
2621.     *mid++= 0;

ffmpeg.c:2621:5: 
2619.         av_exit(1);
2620.     }
2621.     *mid++= 0;
          ^
2622. 
2623.     metadata_count++;
