Viewing epub files leaves /tmp folder littered with 'xreader-nnnn' folders.

Xreader version 2.6.4
Linux Mint 20 Ulyana XFCE

** Steps to reproduce**
Open an epub file. A temporary folder is created of the form '/tmp/xreader-nnnn' where n is a digit. Close xreader. The temporary folder is not removed. Each epub opened creates a new temporary folder that reduces available space in the /tmp folder.

Expected behaviour
Xreader should remove any temporary files when the it exits or an epub is closed.

Other information
Running xreader from a terminal does not result in any errors displayed.

[clefebvre]

EPUB support was removed from Xreader and reimplemented in Xepub: https://github.com/xapp-project/xepub.