plymouth-manager doesn't start

it gives the following output:
Traceback (most recent call last):
  File "plymouth-manager.py", line 23, in <module>
    main.PlymouthManager()
  File "/usr/share/plymouth-manager/src/main.py", line 176, in __init__
    self.getCurrentResolution()
  File "/usr/share/plymouth-manager/src/main.py", line 197, in getCurrentResolution
    self.cmbResolution.set_title(funcmain.getCurrentRes())
TypeError: Gtk.ComboBox.set_title() argument 1 must be string, not None

Thanks for fixing! It's a great tool, and I love it!