ffmpeg.c:2814: error: Null Dereference
  pointer `mid` last assigned on line 2814 could be null and is dereferenced at line 2814, column 5.

ffmpeg.c:2806:1: start of procedure opt_metadata()
2804. }
2805. 
2806. static int opt_metadata(const char *opt, const char *arg)
      ^
2807. {
2808.     char *mid= strchr(arg, '=');

ffmpeg.c:2808:5: 
2806. static int opt_metadata(const char *opt, const char *arg)
2807. {
2808.     char *mid= strchr(arg, '=');
          ^
2809. 
2810.     if(!mid){

ffmpeg.c:2810:9: Taking true branch
2808.     char *mid= strchr(arg, '=');
2809. 
2810.     if(!mid){
              ^
2811.         fprintf(stderr, "Missing =\n");
2812.         ffmpeg_exit(1);

ffmpeg.c:2811:9: 
2809. 
2810.     if(!mid){
2811.         fprintf(stderr, "Missing =\n");
              ^
2812.         ffmpeg_exit(1);
2813.     }

ffmpeg.c:2812:9: Skipping ffmpeg_exit(): empty list of specs
2810.     if(!mid){
2811.         fprintf(stderr, "Missing =\n");
2812.         ffmpeg_exit(1);
              ^
2813.     }
2814.     *mid++= 0;

ffmpeg.c:2814:5: 
2812.         ffmpeg_exit(1);
2813.     }
2814.     *mid++= 0;
          ^
2815. 
2816.     av_metadata_set2(&metadata, arg, mid, 0);
