ffmpeg.c:2600: error: Null Dereference
  pointer `mid` last assigned on line 2600 could be null and is dereferenced at line 2600, column 5.

ffmpeg.c:2592:1: start of procedure opt_metadata()
2590. }
2591. 
2592. static int opt_metadata(const char *opt, const char *arg)
      ^
2593. {
2594.     char *mid= strchr(arg, '=');

ffmpeg.c:2594:5: 
2592. static int opt_metadata(const char *opt, const char *arg)
2593. {
2594.     char *mid= strchr(arg, '=');
          ^
2595. 
2596.     if(!mid){

ffmpeg.c:2596:9: Taking true branch
2594.     char *mid= strchr(arg, '=');
2595. 
2596.     if(!mid){
              ^
2597.         fprintf(stderr, "Missing =\n");
2598.         av_exit(1);

ffmpeg.c:2597:9: 
2595. 
2596.     if(!mid){
2597.         fprintf(stderr, "Missing =\n");
              ^
2598.         av_exit(1);
2599.     }

ffmpeg.c:2598:9: Skipping av_exit(): empty list of specs
2596.     if(!mid){
2597.         fprintf(stderr, "Missing =\n");
2598.         av_exit(1);
              ^
2599.     }
2600.     *mid++= 0;

ffmpeg.c:2600:5: 
2598.         av_exit(1);
2599.     }
2600.     *mid++= 0;
          ^
2601. 
2602.     metadata_count++;
