ffmpeg.c:2631: error: Null Dereference
  pointer `mid` last assigned on line 2631 could be null and is dereferenced at line 2631, column 5.

ffmpeg.c:2623:1: start of procedure opt_metadata()
2621. }
2622. 
2623. static int opt_metadata(const char *opt, const char *arg)
      ^
2624. {
2625.     char *mid= strchr(arg, '=');

ffmpeg.c:2625:5: 
2623. static int opt_metadata(const char *opt, const char *arg)
2624. {
2625.     char *mid= strchr(arg, '=');
          ^
2626. 
2627.     if(!mid){

ffmpeg.c:2627:9: Taking true branch
2625.     char *mid= strchr(arg, '=');
2626. 
2627.     if(!mid){
              ^
2628.         fprintf(stderr, "Missing =\n");
2629.         av_exit(1);

ffmpeg.c:2628:9: 
2626. 
2627.     if(!mid){
2628.         fprintf(stderr, "Missing =\n");
              ^
2629.         av_exit(1);
2630.     }

ffmpeg.c:2629:9: Skipping av_exit(): empty list of specs
2627.     if(!mid){
2628.         fprintf(stderr, "Missing =\n");
2629.         av_exit(1);
              ^
2630.     }
2631.     *mid++= 0;

ffmpeg.c:2631:5: 
2629.         av_exit(1);
2630.     }
2631.     *mid++= 0;
          ^
2632. 
2633.     metadata_count++;
