ffmpeg.c:2743: error: Null Dereference
  pointer `mid` last assigned on line 2743 could be null and is dereferenced at line 2743, column 5.

ffmpeg.c:2735:1: start of procedure opt_metadata()
2733. }
2734. 
2735. static int opt_metadata(const char *opt, const char *arg)
      ^
2736. {
2737.     char *mid= strchr(arg, '=');

ffmpeg.c:2737:5: 
2735. static int opt_metadata(const char *opt, const char *arg)
2736. {
2737.     char *mid= strchr(arg, '=');
          ^
2738. 
2739.     if(!mid){

ffmpeg.c:2739:9: Taking true branch
2737.     char *mid= strchr(arg, '=');
2738. 
2739.     if(!mid){
              ^
2740.         fprintf(stderr, "Missing =\n");
2741.         ffmpeg_exit(1);

ffmpeg.c:2740:9: 
2738. 
2739.     if(!mid){
2740.         fprintf(stderr, "Missing =\n");
              ^
2741.         ffmpeg_exit(1);
2742.     }

ffmpeg.c:2741:9: Skipping ffmpeg_exit(): empty list of specs
2739.     if(!mid){
2740.         fprintf(stderr, "Missing =\n");
2741.         ffmpeg_exit(1);
              ^
2742.     }
2743.     *mid++= 0;

ffmpeg.c:2743:5: 
2741.         ffmpeg_exit(1);
2742.     }
2743.     *mid++= 0;
          ^
2744. 
2745.     av_metadata_set2(&metadata, arg, mid, 0);
