ffmpeg.c:2601: error: Null Dereference
  pointer `mid` last assigned on line 2601 could be null and is dereferenced at line 2601, column 5.

ffmpeg.c:2593:1: start of procedure opt_metadata()
2591. }
2592. 
2593. static int opt_metadata(const char *opt, const char *arg)
      ^
2594. {
2595.     char *mid= strchr(arg, '=');

ffmpeg.c:2595:5: 
2593. static int opt_metadata(const char *opt, const char *arg)
2594. {
2595.     char *mid= strchr(arg, '=');
          ^
2596. 
2597.     if(!mid){

ffmpeg.c:2597:9: Taking true branch
2595.     char *mid= strchr(arg, '=');
2596. 
2597.     if(!mid){
              ^
2598.         fprintf(stderr, "Missing =\n");
2599.         av_exit(1);

ffmpeg.c:2598:9: 
2596. 
2597.     if(!mid){
2598.         fprintf(stderr, "Missing =\n");
              ^
2599.         av_exit(1);
2600.     }

ffmpeg.c:2599:9: Skipping av_exit(): empty list of specs
2597.     if(!mid){
2598.         fprintf(stderr, "Missing =\n");
2599.         av_exit(1);
              ^
2600.     }
2601.     *mid++= 0;

ffmpeg.c:2601:5: 
2599.         av_exit(1);
2600.     }
2601.     *mid++= 0;
          ^
2602. 
2603.     metadata_count++;
