ffmpeg.c:2746: error: Null Dereference
  pointer `mid` last assigned on line 2746 could be null and is dereferenced at line 2746, column 5.

ffmpeg.c:2738:1: start of procedure opt_metadata()
2736. }
2737. 
2738. static int opt_metadata(const char *opt, const char *arg)
      ^
2739. {
2740.     char *mid= strchr(arg, '=');

ffmpeg.c:2740:5: 
2738. static int opt_metadata(const char *opt, const char *arg)
2739. {
2740.     char *mid= strchr(arg, '=');
          ^
2741. 
2742.     if(!mid){

ffmpeg.c:2742:9: Taking true branch
2740.     char *mid= strchr(arg, '=');
2741. 
2742.     if(!mid){
              ^
2743.         fprintf(stderr, "Missing =\n");
2744.         ffmpeg_exit(1);

ffmpeg.c:2743:9: 
2741. 
2742.     if(!mid){
2743.         fprintf(stderr, "Missing =\n");
              ^
2744.         ffmpeg_exit(1);
2745.     }

ffmpeg.c:2744:9: Skipping ffmpeg_exit(): empty list of specs
2742.     if(!mid){
2743.         fprintf(stderr, "Missing =\n");
2744.         ffmpeg_exit(1);
              ^
2745.     }
2746.     *mid++= 0;

ffmpeg.c:2746:5: 
2744.         ffmpeg_exit(1);
2745.     }
2746.     *mid++= 0;
          ^
2747. 
2748.     av_metadata_set2(&metadata, arg, mid, 0);
