ffmpeg.c:2803: error: Null Dereference
  pointer `mid` last assigned on line 2803 could be null and is dereferenced at line 2803, column 5.

ffmpeg.c:2795:1: start of procedure opt_metadata()
2793. }
2794. 
2795. static int opt_metadata(const char *opt, const char *arg)
      ^
2796. {
2797.     char *mid= strchr(arg, '=');

ffmpeg.c:2797:5: 
2795. static int opt_metadata(const char *opt, const char *arg)
2796. {
2797.     char *mid= strchr(arg, '=');
          ^
2798. 
2799.     if(!mid){

ffmpeg.c:2799:9: Taking true branch
2797.     char *mid= strchr(arg, '=');
2798. 
2799.     if(!mid){
              ^
2800.         fprintf(stderr, "Missing =\n");
2801.         ffmpeg_exit(1);

ffmpeg.c:2800:9: 
2798. 
2799.     if(!mid){
2800.         fprintf(stderr, "Missing =\n");
              ^
2801.         ffmpeg_exit(1);
2802.     }

ffmpeg.c:2801:9: Skipping ffmpeg_exit(): empty list of specs
2799.     if(!mid){
2800.         fprintf(stderr, "Missing =\n");
2801.         ffmpeg_exit(1);
              ^
2802.     }
2803.     *mid++= 0;

ffmpeg.c:2803:5: 
2801.         ffmpeg_exit(1);
2802.     }
2803.     *mid++= 0;
          ^
2804. 
2805.     av_metadata_set2(&metadata, arg, mid, 0);
