ffmpeg.c:2813: error: Null Dereference
  pointer `mid` last assigned on line 2813 could be null and is dereferenced at line 2813, column 5.

ffmpeg.c:2805:1: start of procedure opt_metadata()
2803. }
2804. 
2805. static int opt_metadata(const char *opt, const char *arg)
      ^
2806. {
2807.     char *mid= strchr(arg, '=');

ffmpeg.c:2807:5: 
2805. static int opt_metadata(const char *opt, const char *arg)
2806. {
2807.     char *mid= strchr(arg, '=');
          ^
2808. 
2809.     if(!mid){

ffmpeg.c:2809:9: Taking true branch
2807.     char *mid= strchr(arg, '=');
2808. 
2809.     if(!mid){
              ^
2810.         fprintf(stderr, "Missing =\n");
2811.         ffmpeg_exit(1);

ffmpeg.c:2810:9: 
2808. 
2809.     if(!mid){
2810.         fprintf(stderr, "Missing =\n");
              ^
2811.         ffmpeg_exit(1);
2812.     }

ffmpeg.c:2811:9: Skipping ffmpeg_exit(): empty list of specs
2809.     if(!mid){
2810.         fprintf(stderr, "Missing =\n");
2811.         ffmpeg_exit(1);
              ^
2812.     }
2813.     *mid++= 0;

ffmpeg.c:2813:5: 
2811.         ffmpeg_exit(1);
2812.     }
2813.     *mid++= 0;
          ^
2814. 
2815.     av_metadata_set2(&metadata, arg, mid, 0);
