ffmpeg.c:2604: error: Null Dereference
  pointer `mid` last assigned on line 2604 could be null and is dereferenced at line 2604, column 5.

ffmpeg.c:2596:1: start of procedure opt_metadata()
2594. }
2595. 
2596. static int opt_metadata(const char *opt, const char *arg)
      ^
2597. {
2598.     char *mid= strchr(arg, '=');

ffmpeg.c:2598:5: 
2596. static int opt_metadata(const char *opt, const char *arg)
2597. {
2598.     char *mid= strchr(arg, '=');
          ^
2599. 
2600.     if(!mid){

ffmpeg.c:2600:9: Taking true branch
2598.     char *mid= strchr(arg, '=');
2599. 
2600.     if(!mid){
              ^
2601.         fprintf(stderr, "Missing =\n");
2602.         av_exit(1);

ffmpeg.c:2601:9: 
2599. 
2600.     if(!mid){
2601.         fprintf(stderr, "Missing =\n");
              ^
2602.         av_exit(1);
2603.     }

ffmpeg.c:2602:9: Skipping av_exit(): empty list of specs
2600.     if(!mid){
2601.         fprintf(stderr, "Missing =\n");
2602.         av_exit(1);
              ^
2603.     }
2604.     *mid++= 0;

ffmpeg.c:2604:5: 
2602.         av_exit(1);
2603.     }
2604.     *mid++= 0;
          ^
2605. 
2606.     metadata_count++;
