ffmpeg.c:2543: error: Null Dereference
  pointer `mid` last assigned on line 2543 could be null and is dereferenced at line 2543, column 5.

ffmpeg.c:2535:1: start of procedure opt_metadata()
2533. }
2534. 
2535. static int opt_metadata(const char *opt, const char *arg)
      ^
2536. {
2537.     char *mid= strchr(arg, '=');

ffmpeg.c:2537:5: 
2535. static int opt_metadata(const char *opt, const char *arg)
2536. {
2537.     char *mid= strchr(arg, '=');
          ^
2538. 
2539.     if(!mid){

ffmpeg.c:2539:9: Taking true branch
2537.     char *mid= strchr(arg, '=');
2538. 
2539.     if(!mid){
              ^
2540.         fprintf(stderr, "Missing =\n");
2541.         av_exit(1);

ffmpeg.c:2540:9: 
2538. 
2539.     if(!mid){
2540.         fprintf(stderr, "Missing =\n");
              ^
2541.         av_exit(1);
2542.     }

ffmpeg.c:2541:9: Skipping av_exit(): empty list of specs
2539.     if(!mid){
2540.         fprintf(stderr, "Missing =\n");
2541.         av_exit(1);
              ^
2542.     }
2543.     *mid++= 0;

ffmpeg.c:2543:5: 
2541.         av_exit(1);
2542.     }
2543.     *mid++= 0;
          ^
2544. 
2545.     metadata_count++;
