ffmpeg.c:2617: error: Null Dereference
  pointer `mid` last assigned on line 2617 could be null and is dereferenced at line 2617, column 5.

ffmpeg.c:2609:1: start of procedure opt_metadata()
2607. }
2608. 
2609. static int opt_metadata(const char *opt, const char *arg)
      ^
2610. {
2611.     char *mid= strchr(arg, '=');

ffmpeg.c:2611:5: 
2609. static int opt_metadata(const char *opt, const char *arg)
2610. {
2611.     char *mid= strchr(arg, '=');
          ^
2612. 
2613.     if(!mid){

ffmpeg.c:2613:9: Taking true branch
2611.     char *mid= strchr(arg, '=');
2612. 
2613.     if(!mid){
              ^
2614.         fprintf(stderr, "Missing =\n");
2615.         av_exit(1);

ffmpeg.c:2614:9: 
2612. 
2613.     if(!mid){
2614.         fprintf(stderr, "Missing =\n");
              ^
2615.         av_exit(1);
2616.     }

ffmpeg.c:2615:9: Skipping av_exit(): empty list of specs
2613.     if(!mid){
2614.         fprintf(stderr, "Missing =\n");
2615.         av_exit(1);
              ^
2616.     }
2617.     *mid++= 0;

ffmpeg.c:2617:5: 
2615.         av_exit(1);
2616.     }
2617.     *mid++= 0;
          ^
2618. 
2619.     metadata_count++;
