A traceback on creating a new layer:
Traceback (most recent call last):
  File “/Applications/Typotools/RoboFont/RoboFont.app/Contents/Resources/lib/python2.7/vanilla/vanillaBase.py”, line 196, in action_
    self.callback(sender)
  File “lib/UI/newLayerSheet.pyc”, line 53, in addCallback
  File “lib/fontObjects/doodleFont.pyc”, line 97, in createLayer
  File “/Applications/Typotools/RoboFont/RoboFont.app/Contents/Resources/lib/python2.7/defcon/tools/notifications.py”, line 125, in postNotification
    callback = getattr(observer, methodName)
AttributeError: ‘NoneType’ object has no attribute ‘action’
Traceback (most recent call last):
  File “lib/doodleDelegate.pyc”, line 65, in sendEvent_
  File “/Applications/Typotools/RoboFont/RoboFont.app/Contents/Resources/lib/python2.7/vanilla/vanillaBase.py”, line 196, in action_
    self.callback(sender)
  File “lib/UI/newLayerSheet.pyc”, line 53, in addCallback
  File “lib/fontObjects/doodleFont.pyc”, line 97, in createLayer
  File “/Applications/Typotools/RoboFont/RoboFont.app/Contents/Resources/lib/python2.7/defcon/tools/notifications.py”, line 125, in postNotification
    callback = getattr(observer, methodName)
AttributeError: ‘NoneType’ object has no attribute ‘action’