ffmpeg.c:2674: error: Null Dereference
  pointer `mid` last assigned on line 2674 could be null and is dereferenced at line 2674, column 5.

ffmpeg.c:2666:1: start of procedure opt_metadata()
2664. }
2665. 
2666. static int opt_metadata(const char *opt, const char *arg)
      ^
2667. {
2668.     char *mid= strchr(arg, '=');

ffmpeg.c:2668:5: 
2666. static int opt_metadata(const char *opt, const char *arg)
2667. {
2668.     char *mid= strchr(arg, '=');
          ^
2669. 
2670.     if(!mid){

ffmpeg.c:2670:9: Taking true branch
2668.     char *mid= strchr(arg, '=');
2669. 
2670.     if(!mid){
              ^
2671.         fprintf(stderr, "Missing =\n");
2672.         av_exit(1);

ffmpeg.c:2671:9: 
2669. 
2670.     if(!mid){
2671.         fprintf(stderr, "Missing =\n");
              ^
2672.         av_exit(1);
2673.     }

ffmpeg.c:2672:9: Skipping av_exit(): empty list of specs
2670.     if(!mid){
2671.         fprintf(stderr, "Missing =\n");
2672.         av_exit(1);
              ^
2673.     }
2674.     *mid++= 0;

ffmpeg.c:2674:5: 
2672.         av_exit(1);
2673.     }
2674.     *mid++= 0;
          ^
2675. 
2676.     metadata_count++;
