ffmpeg.c:1095: error: Null Dereference
  pointer `vstats_file` last assigned on line 1085 could be null and is dereferenced by call to `fprintf()` at line 1095, column 9.

ffmpeg.c:1076:1: start of procedure do_video_stats()
1074. }
1075. 
1076. static void do_video_stats(AVFormatContext *os, AVOutputStream *ost,
      ^
1077.                            int frame_size)
1078. {

ffmpeg.c:1084:10: Taking true branch
1082. 
1083.     /* this is executed just the first time do_video_stats is called */
1084.     if (!vstats_file) {
               ^
1085.         vstats_file = fopen(vstats_filename, "w");
1086.         if (!vstats_file) {

ffmpeg.c:1085:9: 
1083.     /* this is executed just the first time do_video_stats is called */
1084.     if (!vstats_file) {
1085.         vstats_file = fopen(vstats_filename, "w");
              ^
1086.         if (!vstats_file) {
1087.             perror("fopen");

ffmpeg.c:1086:14: Taking true branch
1084.     if (!vstats_file) {
1085.         vstats_file = fopen(vstats_filename, "w");
1086.         if (!vstats_file) {
                   ^
1087.             perror("fopen");
1088.             av_exit(1);

ffmpeg.c:1087:13: 
1085.         vstats_file = fopen(vstats_filename, "w");
1086.         if (!vstats_file) {
1087.             perror("fopen");
                  ^
1088.             av_exit(1);
1089.         }

ffmpeg.c:1088:13: Skipping av_exit(): empty list of specs
1086.         if (!vstats_file) {
1087.             perror("fopen");
1088.             av_exit(1);
                  ^
1089.         }
1090.     }

ffmpeg.c:1092:5: 
1090.     }
1091. 
1092.     enc = ost->st->codec;
          ^
1093.     if (enc->codec_type == CODEC_TYPE_VIDEO) {
1094.         frame_number = ost->frame_number;

ffmpeg.c:1093:9: Taking true branch
1091. 
1092.     enc = ost->st->codec;
1093.     if (enc->codec_type == CODEC_TYPE_VIDEO) {
              ^
1094.         frame_number = ost->frame_number;
1095.         fprintf(vstats_file, "frame= %5d q= %2.1f ", frame_number, enc->coded_frame->quality/(float)FF_QP2LAMBDA);

ffmpeg.c:1094:9: 
1092.     enc = ost->st->codec;
1093.     if (enc->codec_type == CODEC_TYPE_VIDEO) {
1094.         frame_number = ost->frame_number;
              ^
1095.         fprintf(vstats_file, "frame= %5d q= %2.1f ", frame_number, enc->coded_frame->quality/(float)FF_QP2LAMBDA);
1096.         if (enc->flags&CODEC_FLAG_PSNR)

ffmpeg.c:1095:9: 
1093.     if (enc->codec_type == CODEC_TYPE_VIDEO) {
1094.         frame_number = ost->frame_number;
1095.         fprintf(vstats_file, "frame= %5d q= %2.1f ", frame_number, enc->coded_frame->quality/(float)FF_QP2LAMBDA);
              ^
1096.         if (enc->flags&CODEC_FLAG_PSNR)
1097.             fprintf(vstats_file, "PSNR= %6.2f ", psnr(enc->coded_frame->error[0]/(enc->width*enc->height*255.0*255.0)));
