ffmpeg.c:2788: error: Null Dereference
  pointer `mid` last assigned on line 2788 could be null and is dereferenced at line 2788, column 5.

ffmpeg.c:2780:1: start of procedure opt_metadata()
2778. }
2779. 
2780. static int opt_metadata(const char *opt, const char *arg)
      ^
2781. {
2782.     char *mid= strchr(arg, '=');

ffmpeg.c:2782:5: 
2780. static int opt_metadata(const char *opt, const char *arg)
2781. {
2782.     char *mid= strchr(arg, '=');
          ^
2783. 
2784.     if(!mid){

ffmpeg.c:2784:9: Taking true branch
2782.     char *mid= strchr(arg, '=');
2783. 
2784.     if(!mid){
              ^
2785.         fprintf(stderr, "Missing =\n");
2786.         ffmpeg_exit(1);

ffmpeg.c:2785:9: 
2783. 
2784.     if(!mid){
2785.         fprintf(stderr, "Missing =\n");
              ^
2786.         ffmpeg_exit(1);
2787.     }

ffmpeg.c:2786:9: Skipping ffmpeg_exit(): empty list of specs
2784.     if(!mid){
2785.         fprintf(stderr, "Missing =\n");
2786.         ffmpeg_exit(1);
              ^
2787.     }
2788.     *mid++= 0;

ffmpeg.c:2788:5: 
2786.         ffmpeg_exit(1);
2787.     }
2788.     *mid++= 0;
          ^
2789. 
2790.     av_metadata_set2(&metadata, arg, mid, 0);
