uncaught error on sbackup when choosing backup directory

[alfed neuman]

system: Linux Mint 15 (Olivia) 32-bit
version: Simple Backup Suite 0.11.4
installed from Software Manager

Simple Backup-configuration (non-admins)>Destination>Use custom local backup directory
produces this error message:

"Sorry, this should not have happened

An uncaught error occurred. Close this message window and restart the application.

Please report this error on https://bugs.launchpad.net/sbackup.

coercing to Unicode: need string or buffer, NoneType found

Traceback (most recent call last):
  File "/usr/share/sbackup/sbackup/ui/configgui.py", line 1103, in on_dest1_toggled
    self.on_dest_localpath_selection_changed()
  File "/usr/share/sbackup/sbackup/ui/configgui.py", line 1542, in on_dest_localpath_selection_changed
    if (os.path.isdir(_target) and os.access(_target, os.R_OK | os.W_OK | os.X_OK)):
  File "/usr/lib/python2.7/genericpath.py", line 41, in isdir
    st = os.stat(s)
TypeError: coercing to Unicode: need string or buffer, NoneType found"

A restart produces the same effect.

[Zickzackzuck (therkcompany)]

Ubuntu-GNOME 13.04

Simple Backup Suite 0.11.4

Same procedure as explained above.

Following Error occurs:

"Entschuldigung, das hätte nicht passieren dürfen

Ein unbekannter Fehler ist aufgetreten. Schließen Sie dieses Fenster und starten Sie die Anwendung neu.

Bitte melden Sie diesen Fehler unter: https://bugs.launchpad.net/sbackup.

coercing to Unicode: need string or buffer, NoneType found

Traceback (most recent call last):
  File "/usr/share/sbackup/sbackup/ui/configgui.py", line 1103, in on_dest1_toggled
    self.on_dest_localpath_selection_changed()
  File "/usr/share/sbackup/sbackup/ui/configgui.py", line 1542, in on_dest_localpath_selection_changed
    if (os.path.isdir(_target) and os.access(_target, os.R_OK | os.W_OK | os.X_OK)):
  File "/usr/lib/python2.7/genericpath.py", line 41, in isdir
    st = os.stat(s)
TypeError: coercing to Unicode: need string or buffer, NoneType found"