I'm not good at reporting bug, and pardon my english.

This bug is easy to do.

Open tmp diretory(or any) thunar.
On terminal, do `echo "test" > /tmp/test ; shred -u /tmp/test`


Environment
```
me@localhost:# thunar --version
Thunar 1.6.11 (Xfce 4.12)

Copyright (c) 2004-2015
	The Thunar development team. All rights reserved.

Written by Benedikt Meurer <benny@xfce.org>.

Please report bugs to <http://bugzilla.xfce.org/>.
me@localhost:# uname -a
Linux localhost 4.9.0-3-amd64 #1 SMP Debian 4.9.30-2+deb9u3 (2017-08-06) x86_64 GNU/Linux
```