ffmpeg.c:2704: error: Null Dereference
  pointer `mid` last assigned on line 2704 could be null and is dereferenced at line 2704, column 5.

ffmpeg.c:2696:1: start of procedure opt_metadata()
2694. }
2695. 
2696. static int opt_metadata(const char *opt, const char *arg)
      ^
2697. {
2698.     char *mid= strchr(arg, '=');

ffmpeg.c:2698:5: 
2696. static int opt_metadata(const char *opt, const char *arg)
2697. {
2698.     char *mid= strchr(arg, '=');
          ^
2699. 
2700.     if(!mid){

ffmpeg.c:2700:9: Taking true branch
2698.     char *mid= strchr(arg, '=');
2699. 
2700.     if(!mid){
              ^
2701.         fprintf(stderr, "Missing =\n");
2702.         av_exit(1);

ffmpeg.c:2701:9: 
2699. 
2700.     if(!mid){
2701.         fprintf(stderr, "Missing =\n");
              ^
2702.         av_exit(1);
2703.     }

ffmpeg.c:2702:9: Skipping av_exit(): empty list of specs
2700.     if(!mid){
2701.         fprintf(stderr, "Missing =\n");
2702.         av_exit(1);
              ^
2703.     }
2704.     *mid++= 0;

ffmpeg.c:2704:5: 
2702.         av_exit(1);
2703.     }
2704.     *mid++= 0;
          ^
2705. 
2706.     metadata_count++;
