ffmpeg.c:2610: error: Null Dereference
  pointer `mid` last assigned on line 2610 could be null and is dereferenced at line 2610, column 5.

ffmpeg.c:2602:1: start of procedure opt_metadata()
2600. }
2601. 
2602. static int opt_metadata(const char *opt, const char *arg)
      ^
2603. {
2604.     char *mid= strchr(arg, '=');

ffmpeg.c:2604:5: 
2602. static int opt_metadata(const char *opt, const char *arg)
2603. {
2604.     char *mid= strchr(arg, '=');
          ^
2605. 
2606.     if(!mid){

ffmpeg.c:2606:9: Taking true branch
2604.     char *mid= strchr(arg, '=');
2605. 
2606.     if(!mid){
              ^
2607.         fprintf(stderr, "Missing =\n");
2608.         av_exit(1);

ffmpeg.c:2607:9: 
2605. 
2606.     if(!mid){
2607.         fprintf(stderr, "Missing =\n");
              ^
2608.         av_exit(1);
2609.     }

ffmpeg.c:2608:9: Skipping av_exit(): empty list of specs
2606.     if(!mid){
2607.         fprintf(stderr, "Missing =\n");
2608.         av_exit(1);
              ^
2609.     }
2610.     *mid++= 0;

ffmpeg.c:2610:5: 
2608.         av_exit(1);
2609.     }
2610.     *mid++= 0;
          ^
2611. 
2612.     metadata_count++;
