ffmpeg.c:1141: error: Null Dereference
  pointer `vstats_file` last assigned on line 1131 could be null and is dereferenced by call to `fprintf()` at line 1141, column 9.

ffmpeg.c:1122:1: start of procedure do_video_stats()
1120. }
1121. 
1122. static void do_video_stats(AVFormatContext *os, AVOutputStream *ost,
      ^
1123.                            int frame_size)
1124. {

ffmpeg.c:1130:10: Taking true branch
1128. 
1129.     /* this is executed just the first time do_video_stats is called */
1130.     if (!vstats_file) {
               ^
1131.         vstats_file = fopen(vstats_filename, "w");
1132.         if (!vstats_file) {

ffmpeg.c:1131:9: 
1129.     /* this is executed just the first time do_video_stats is called */
1130.     if (!vstats_file) {
1131.         vstats_file = fopen(vstats_filename, "w");
              ^
1132.         if (!vstats_file) {
1133.             perror("fopen");

ffmpeg.c:1132:14: Taking true branch
1130.     if (!vstats_file) {
1131.         vstats_file = fopen(vstats_filename, "w");
1132.         if (!vstats_file) {
                   ^
1133.             perror("fopen");
1134.             av_exit(1);

ffmpeg.c:1133:13: 
1131.         vstats_file = fopen(vstats_filename, "w");
1132.         if (!vstats_file) {
1133.             perror("fopen");
                  ^
1134.             av_exit(1);
1135.         }

ffmpeg.c:1134:13: Skipping av_exit(): empty list of specs
1132.         if (!vstats_file) {
1133.             perror("fopen");
1134.             av_exit(1);
                  ^
1135.         }
1136.     }

ffmpeg.c:1138:5: 
1136.     }
1137. 
1138.     enc = ost->st->codec;
          ^
1139.     if (enc->codec_type == CODEC_TYPE_VIDEO) {
1140.         frame_number = ost->frame_number;

ffmpeg.c:1139:9: Taking true branch
1137. 
1138.     enc = ost->st->codec;
1139.     if (enc->codec_type == CODEC_TYPE_VIDEO) {
              ^
1140.         frame_number = ost->frame_number;
1141.         fprintf(vstats_file, "frame= %5d q= %2.1f ", frame_number, enc->coded_frame->quality/(float)FF_QP2LAMBDA);

ffmpeg.c:1140:9: 
1138.     enc = ost->st->codec;
1139.     if (enc->codec_type == CODEC_TYPE_VIDEO) {
1140.         frame_number = ost->frame_number;
              ^
1141.         fprintf(vstats_file, "frame= %5d q= %2.1f ", frame_number, enc->coded_frame->quality/(float)FF_QP2LAMBDA);
1142.         if (enc->flags&CODEC_FLAG_PSNR)

ffmpeg.c:1141:9: 
1139.     if (enc->codec_type == CODEC_TYPE_VIDEO) {
1140.         frame_number = ost->frame_number;
1141.         fprintf(vstats_file, "frame= %5d q= %2.1f ", frame_number, enc->coded_frame->quality/(float)FF_QP2LAMBDA);
              ^
1142.         if (enc->flags&CODEC_FLAG_PSNR)
1143.             fprintf(vstats_file, "PSNR= %6.2f ", psnr(enc->coded_frame->error[0]/(enc->width*enc->height*255.0*255.0)));
