ffmpeg.c:2579: error: Null Dereference
  pointer `mid` last assigned on line 2579 could be null and is dereferenced at line 2579, column 5.

ffmpeg.c:2571:1: start of procedure opt_metadata()
2569. }
2570. 
2571. static int opt_metadata(const char *opt, const char *arg)
      ^
2572. {
2573.     char *mid= strchr(arg, '=');

ffmpeg.c:2573:5: 
2571. static int opt_metadata(const char *opt, const char *arg)
2572. {
2573.     char *mid= strchr(arg, '=');
          ^
2574. 
2575.     if(!mid){

ffmpeg.c:2575:9: Taking true branch
2573.     char *mid= strchr(arg, '=');
2574. 
2575.     if(!mid){
              ^
2576.         fprintf(stderr, "Missing =\n");
2577.         av_exit(1);

ffmpeg.c:2576:9: 
2574. 
2575.     if(!mid){
2576.         fprintf(stderr, "Missing =\n");
              ^
2577.         av_exit(1);
2578.     }

ffmpeg.c:2577:9: Skipping av_exit(): empty list of specs
2575.     if(!mid){
2576.         fprintf(stderr, "Missing =\n");
2577.         av_exit(1);
              ^
2578.     }
2579.     *mid++= 0;

ffmpeg.c:2579:5: 
2577.         av_exit(1);
2578.     }
2579.     *mid++= 0;
          ^
2580. 
2581.     metadata_count++;
