Cannot close Options window by Cancel

[Nick]

Xubuntu 17.04
Zim 0.66

Menu: Edit - Options - see options window.
Click on "Cancel"-button - and appear error-message:

"This is zim 0.66
Platform: posix
Locale: ru_RU UTF-8
FS encoding: UTF-8
Python: (2, 7, 13, 'final', 0)
Gtk: (2, 24, 31)
Pygtk: (2, 24, 0)
No bzr version-info found

======= Traceback =======
  File "/usr/lib/python2.7/dist-packages/zim/gui/widgets.py", line 3205, in do_response
    destroy = self.do_response_cancel()
  File "/usr/lib/python2.7/dist-packages/zim/gui/preferencesdialog.py", line 165, in do_response_cancel
    activatable = klass.check_dependencies_ok()
  File "/usr/lib/python2.7/dist-packages/zim/plugins/__init__.py", line 412, in check_dependencies_ok
    check, dependencies = klass.check_dependencies()
  File "/home/nick/.local/share/zim/plugins/thememanager.py", line 95, in check_dependencies
    return (os_windows and zim_windows and program_files), \
UnboundLocalError: local variable 'os_windows' referenced before assignment"

I can close options window only by "OK"-button.

[Jaap Karssenberg (jaap.karssenberg)]

Error in unsupported plugin - but will need to make dialog robust for such error