.tar.bz2 extension added whatever the file name

Hi,

When you export a configuration, the .tar.bz2 extension added whatever the filename is entered by the user in the save dialogbox.

So if, for instance, instead of entering a name manually, I select an existing filename (because I want to overwrite an old backup of a config), I end up

1. with the old backup not being overwritten and
2. with a new file with filename containing .tar.bz2.tar.bz2 ...

Not exactly what the user wants...