ffmpeg.c:2716: error: Null Dereference
  pointer `mid` last assigned on line 2716 could be null and is dereferenced at line 2716, column 5.

ffmpeg.c:2708:1: start of procedure opt_metadata()
2706. }
2707. 
2708. static int opt_metadata(const char *opt, const char *arg)
      ^
2709. {
2710.     char *mid= strchr(arg, '=');

ffmpeg.c:2710:5: 
2708. static int opt_metadata(const char *opt, const char *arg)
2709. {
2710.     char *mid= strchr(arg, '=');
          ^
2711. 
2712.     if(!mid){

ffmpeg.c:2712:9: Taking true branch
2710.     char *mid= strchr(arg, '=');
2711. 
2712.     if(!mid){
              ^
2713.         fprintf(stderr, "Missing =\n");
2714.         av_exit(1);

ffmpeg.c:2713:9: 
2711. 
2712.     if(!mid){
2713.         fprintf(stderr, "Missing =\n");
              ^
2714.         av_exit(1);
2715.     }

ffmpeg.c:2714:9: Skipping av_exit(): empty list of specs
2712.     if(!mid){
2713.         fprintf(stderr, "Missing =\n");
2714.         av_exit(1);
              ^
2715.     }
2716.     *mid++= 0;

ffmpeg.c:2716:5: 
2714.         av_exit(1);
2715.     }
2716.     *mid++= 0;
          ^
2717. 
2718.     metadata_count++;
