ffmpeg.c:2624: error: Null Dereference
  pointer `mid` last assigned on line 2624 could be null and is dereferenced at line 2624, column 5.

ffmpeg.c:2616:1: start of procedure opt_metadata()
2614. }
2615. 
2616. static int opt_metadata(const char *opt, const char *arg)
      ^
2617. {
2618.     char *mid= strchr(arg, '=');

ffmpeg.c:2618:5: 
2616. static int opt_metadata(const char *opt, const char *arg)
2617. {
2618.     char *mid= strchr(arg, '=');
          ^
2619. 
2620.     if(!mid){

ffmpeg.c:2620:9: Taking true branch
2618.     char *mid= strchr(arg, '=');
2619. 
2620.     if(!mid){
              ^
2621.         fprintf(stderr, "Missing =\n");
2622.         av_exit(1);

ffmpeg.c:2621:9: 
2619. 
2620.     if(!mid){
2621.         fprintf(stderr, "Missing =\n");
              ^
2622.         av_exit(1);
2623.     }

ffmpeg.c:2622:9: Skipping av_exit(): empty list of specs
2620.     if(!mid){
2621.         fprintf(stderr, "Missing =\n");
2622.         av_exit(1);
              ^
2623.     }
2624.     *mid++= 0;

ffmpeg.c:2624:5: 
2622.         av_exit(1);
2623.     }
2624.     *mid++= 0;
          ^
2625. 
2626.     metadata_count++;
