ffmpeg.c:2613: error: Null Dereference
  pointer `mid` last assigned on line 2613 could be null and is dereferenced at line 2613, column 5.

ffmpeg.c:2605:1: start of procedure opt_metadata()
2603. }
2604. 
2605. static int opt_metadata(const char *opt, const char *arg)
      ^
2606. {
2607.     char *mid= strchr(arg, '=');

ffmpeg.c:2607:5: 
2605. static int opt_metadata(const char *opt, const char *arg)
2606. {
2607.     char *mid= strchr(arg, '=');
          ^
2608. 
2609.     if(!mid){

ffmpeg.c:2609:9: Taking true branch
2607.     char *mid= strchr(arg, '=');
2608. 
2609.     if(!mid){
              ^
2610.         fprintf(stderr, "Missing =\n");
2611.         av_exit(1);

ffmpeg.c:2610:9: 
2608. 
2609.     if(!mid){
2610.         fprintf(stderr, "Missing =\n");
              ^
2611.         av_exit(1);
2612.     }

ffmpeg.c:2611:9: Skipping av_exit(): empty list of specs
2609.     if(!mid){
2610.         fprintf(stderr, "Missing =\n");
2611.         av_exit(1);
              ^
2612.     }
2613.     *mid++= 0;

ffmpeg.c:2613:5: 
2611.         av_exit(1);
2612.     }
2613.     *mid++= 0;
          ^
2614. 
2615.     metadata_count++;
