ffmpeg.c:2742: error: Null Dereference
  pointer `mid` last assigned on line 2742 could be null and is dereferenced at line 2742, column 5.

ffmpeg.c:2734:1: start of procedure opt_metadata()
2732. }
2733. 
2734. static int opt_metadata(const char *opt, const char *arg)
      ^
2735. {
2736.     char *mid= strchr(arg, '=');

ffmpeg.c:2736:5: 
2734. static int opt_metadata(const char *opt, const char *arg)
2735. {
2736.     char *mid= strchr(arg, '=');
          ^
2737. 
2738.     if(!mid){

ffmpeg.c:2738:9: Taking true branch
2736.     char *mid= strchr(arg, '=');
2737. 
2738.     if(!mid){
              ^
2739.         fprintf(stderr, "Missing =\n");
2740.         ffmpeg_exit(1);

ffmpeg.c:2739:9: 
2737. 
2738.     if(!mid){
2739.         fprintf(stderr, "Missing =\n");
              ^
2740.         ffmpeg_exit(1);
2741.     }

ffmpeg.c:2740:9: Skipping ffmpeg_exit(): empty list of specs
2738.     if(!mid){
2739.         fprintf(stderr, "Missing =\n");
2740.         ffmpeg_exit(1);
              ^
2741.     }
2742.     *mid++= 0;

ffmpeg.c:2742:5: 
2740.         ffmpeg_exit(1);
2741.     }
2742.     *mid++= 0;
          ^
2743. 
2744.     av_metadata_set2(&metadata, arg, mid, 0);
