"size unknown" for .txt files

[Gfy]

https://bitbucket.org/Gfy/pyrescene/issues/83/correct-size-info-for-broken-mkv-sample

Broken .mkv files that have the correct size but are corrupt internally, will show the expected size in the error message now. (.txt)

Show the proper size instead of "size unknown".

Example: http://www.srrdb.com/release/details/UFO.S01E24.Reflections.in.the.Water.720p.BluRay.x264-iFPD