ffmpeg.c:2629: error: Null Dereference
  pointer `mid` last assigned on line 2629 could be null and is dereferenced at line 2629, column 5.

ffmpeg.c:2621:1: start of procedure opt_metadata()
2619. }
2620. 
2621. static int opt_metadata(const char *opt, const char *arg)
      ^
2622. {
2623.     char *mid= strchr(arg, '=');

ffmpeg.c:2623:5: 
2621. static int opt_metadata(const char *opt, const char *arg)
2622. {
2623.     char *mid= strchr(arg, '=');
          ^
2624. 
2625.     if(!mid){

ffmpeg.c:2625:9: Taking true branch
2623.     char *mid= strchr(arg, '=');
2624. 
2625.     if(!mid){
              ^
2626.         fprintf(stderr, "Missing =\n");
2627.         av_exit(1);

ffmpeg.c:2626:9: 
2624. 
2625.     if(!mid){
2626.         fprintf(stderr, "Missing =\n");
              ^
2627.         av_exit(1);
2628.     }

ffmpeg.c:2627:9: Skipping av_exit(): empty list of specs
2625.     if(!mid){
2626.         fprintf(stderr, "Missing =\n");
2627.         av_exit(1);
              ^
2628.     }
2629.     *mid++= 0;

ffmpeg.c:2629:5: 
2627.         av_exit(1);
2628.     }
2629.     *mid++= 0;
          ^
2630. 
2631.     metadata_count++;
