ffmpeg.c:2858: error: Null Dereference
  pointer `mid` last assigned on line 2858 could be null and is dereferenced at line 2858, column 5.

ffmpeg.c:2850:1: start of procedure opt_metadata()
2848. }
2849. 
2850. static int opt_metadata(const char *opt, const char *arg)
      ^
2851. {
2852.     char *mid= strchr(arg, '=');

ffmpeg.c:2852:5: 
2850. static int opt_metadata(const char *opt, const char *arg)
2851. {
2852.     char *mid= strchr(arg, '=');
          ^
2853. 
2854.     if(!mid){

ffmpeg.c:2854:9: Taking true branch
2852.     char *mid= strchr(arg, '=');
2853. 
2854.     if(!mid){
              ^
2855.         fprintf(stderr, "Missing =\n");
2856.         ffmpeg_exit(1);

ffmpeg.c:2855:9: 
2853. 
2854.     if(!mid){
2855.         fprintf(stderr, "Missing =\n");
              ^
2856.         ffmpeg_exit(1);
2857.     }

ffmpeg.c:2856:9: Skipping ffmpeg_exit(): empty list of specs
2854.     if(!mid){
2855.         fprintf(stderr, "Missing =\n");
2856.         ffmpeg_exit(1);
              ^
2857.     }
2858.     *mid++= 0;

ffmpeg.c:2858:5: 
2856.         ffmpeg_exit(1);
2857.     }
2858.     *mid++= 0;
          ^
2859. 
2860.     av_dict_set(&metadata, arg, mid, 0);

static int opt_metadata(const char *opt, const char *arg)
{
    char *mid= strchr(arg, '=');
    if(!mid){
        fprintf(stderr, "Missing =\n");
        ffmpeg_exit(1);
    }
    *mid++= 0;
    av_dict_set(&metadata, arg, mid, 0);
    return 0;
}
['static int opt_metadata(const char *opt, const char *arg)\n{\n    char *mid= strchr(arg, \'=\');\n    if(!mid){\n        fprintf(stderr, "Missing =\\n");\n        ffmpeg_exit(1);\n    }\n    *mid++= 0;\n    av_dict_set(&metadata, arg, mid, 0);\n    return 0;\n}']