ffmpeg.c:2818: error: Null Dereference
  pointer `mid` last assigned on line 2818 could be null and is dereferenced at line 2818, column 5.

ffmpeg.c:2810:1: start of procedure opt_metadata()
2808. }
2809. 
2810. static int opt_metadata(const char *opt, const char *arg)
      ^
2811. {
2812.     char *mid= strchr(arg, '=');

ffmpeg.c:2812:5: 
2810. static int opt_metadata(const char *opt, const char *arg)
2811. {
2812.     char *mid= strchr(arg, '=');
          ^
2813. 
2814.     if(!mid){

ffmpeg.c:2814:9: Taking true branch
2812.     char *mid= strchr(arg, '=');
2813. 
2814.     if(!mid){
              ^
2815.         fprintf(stderr, "Missing =\n");
2816.         ffmpeg_exit(1);

ffmpeg.c:2815:9: 
2813. 
2814.     if(!mid){
2815.         fprintf(stderr, "Missing =\n");
              ^
2816.         ffmpeg_exit(1);
2817.     }

ffmpeg.c:2816:9: Skipping ffmpeg_exit(): empty list of specs
2814.     if(!mid){
2815.         fprintf(stderr, "Missing =\n");
2816.         ffmpeg_exit(1);
              ^
2817.     }
2818.     *mid++= 0;

ffmpeg.c:2818:5: 
2816.         ffmpeg_exit(1);
2817.     }
2818.     *mid++= 0;
          ^
2819. 
2820.     av_metadata_set2(&metadata, arg, mid, 0);
