ffmpeg.c:2645: error: Null Dereference
  pointer `mid` last assigned on line 2645 could be null and is dereferenced at line 2645, column 5.

ffmpeg.c:2637:1: start of procedure opt_metadata()
2635. }
2636. 
2637. static int opt_metadata(const char *opt, const char *arg)
      ^
2638. {
2639.     char *mid= strchr(arg, '=');

ffmpeg.c:2639:5: 
2637. static int opt_metadata(const char *opt, const char *arg)
2638. {
2639.     char *mid= strchr(arg, '=');
          ^
2640. 
2641.     if(!mid){

ffmpeg.c:2641:9: Taking true branch
2639.     char *mid= strchr(arg, '=');
2640. 
2641.     if(!mid){
              ^
2642.         fprintf(stderr, "Missing =\n");
2643.         av_exit(1);

ffmpeg.c:2642:9: 
2640. 
2641.     if(!mid){
2642.         fprintf(stderr, "Missing =\n");
              ^
2643.         av_exit(1);
2644.     }

ffmpeg.c:2643:9: Skipping av_exit(): empty list of specs
2641.     if(!mid){
2642.         fprintf(stderr, "Missing =\n");
2643.         av_exit(1);
              ^
2644.     }
2645.     *mid++= 0;

ffmpeg.c:2645:5: 
2643.         av_exit(1);
2644.     }
2645.     *mid++= 0;
          ^
2646. 
2647.     metadata_count++;
