Bugs with forced use of ffmpeg presets
Commit 409adbc952de introduced presets to work around ffmpeg x264 issues(?). Using mpeg4 as codec transcode now is trying to load (export/export_ffmpeg.c line 308) a file medium.ffpreset (defined in export/ffmpeg_cfg.c line 129), which normally doesn't exists. So it exits ( export/export_ffmpeg.c line 325) via av_exit (line 204) which frees at least 'video_codec_name' which has not been allocated, so glibc vows. if that file medium.ffpreset exists but is empty, another bug is triggered at line 330.