ffmpeg.c:2608: error: Null Dereference
  pointer `mid` last assigned on line 2608 could be null and is dereferenced at line 2608, column 5.

ffmpeg.c:2600:1: start of procedure opt_metadata()
2598. }
2599. 
2600. static int opt_metadata(const char *opt, const char *arg)
      ^
2601. {
2602.     char *mid= strchr(arg, '=');

ffmpeg.c:2602:5: 
2600. static int opt_metadata(const char *opt, const char *arg)
2601. {
2602.     char *mid= strchr(arg, '=');
          ^
2603. 
2604.     if(!mid){

ffmpeg.c:2604:9: Taking true branch
2602.     char *mid= strchr(arg, '=');
2603. 
2604.     if(!mid){
              ^
2605.         fprintf(stderr, "Missing =\n");
2606.         av_exit(1);

ffmpeg.c:2605:9: 
2603. 
2604.     if(!mid){
2605.         fprintf(stderr, "Missing =\n");
              ^
2606.         av_exit(1);
2607.     }

ffmpeg.c:2606:9: Skipping av_exit(): empty list of specs
2604.     if(!mid){
2605.         fprintf(stderr, "Missing =\n");
2606.         av_exit(1);
              ^
2607.     }
2608.     *mid++= 0;

ffmpeg.c:2608:5: 
2606.         av_exit(1);
2607.     }
2608.     *mid++= 0;
          ^
2609. 
2610.     metadata_count++;
