Cuboid Clone

trying to save gives me a error in the last version currently available:

Traceback (most recent call last):
  File "/Applications/Panda3D/1.7.0/lib/direct/showbase/EventManager.py", line 61, in eventLoopTask
    self.doEvents()
  File "/Applications/Panda3D/1.7.0/lib/direct/showbase/EventManager.py", line 55, in doEvents
    processFunc(self.eventQueue.dequeueEvent())
  File "/Applications/Panda3D/1.7.0/lib/direct/showbase/EventManager.py", line 122, in processEvent
    messenger.send(eventName, paramList)
  File "/Applications/Panda3D/1.7.0/lib/direct/showbase/Messenger.py", line 325, in send
    self.__dispatch(acceptorDict, event, sentArgs, foundWatch)
  File "/Applications/Panda3D/1.7.0/lib/direct/showbase/Messenger.py", line 410, in __dispatch
    method (*(extraArgs + sentArgs))
  File "/Applications/Panda3D/1.7.0/lib/direct/gui/DirectButton.py", line 103, in commandFunc
    apply(self['command'], self['extraArgs'])
  File "/Users/rspoerri/Downloads/Cuboid-Clone 3/cuboid.py", line 226, in savemap
    if i < xmin:
UnboundLocalError: local variable 'xmin' referenced before assignment
:task(error): Exception occurred in PythonTask eventManager
Traceback (most recent call last):
  File "/Users/rspoerri/Downloads/Cuboid-Clone 3/cuboid.py", line 620, in <module>
    run()
  File "/Applications/Panda3D/1.7.0/lib/direct/showbase/ShowBase.py", line 2478, in run
    self.taskMgr.run()
  File "/Applications/Panda3D/1.7.0/lib/direct/task/Task.py", line 482, in run
    self.step()
  File "/Applications/Panda3D/1.7.0/lib/direct/task/Task.py", line 440, in step
    self.mgr.poll()
  File "/Applications/Panda3D/1.7.0/lib/direct/showbase/EventManager.py", line 61, in eventLoopTask
    self.doEvents()
  File "/Applications/Panda3D/1.7.0/lib/direct/showbase/EventManager.py", line 55, in doEvents
    processFunc(self.eventQueue.dequeueEvent())
  File "/Applications/Panda3D/1.7.0/lib/direct/showbase/EventManager.py", line 122, in processEvent
    messenger.send(eventName, paramList)
  File "/Applications/Panda3D/1.7.0/lib/direct/showbase/Messenger.py", line 325, in send
    self.__dispatch(acceptorDict, event, sentArgs, foundWatch)
  File "/Applications/Panda3D/1.7.0/lib/direct/showbase/Messenger.py", line 410, in __dispatch
    method (*(extraArgs + sentArgs))
  File "/Applications/Panda3D/1.7.0/lib/direct/gui/DirectButton.py", line 103, in commandFunc
    apply(self['command'], self['extraArgs'])
  File "/Users/rspoerri/Downloads/Cuboid-Clone 3/cuboid.py", line 226, in savemap
    if i < xmin:
UnboundLocalError: local variable 'xmin' referenced before assignment
Wed Oct 21 16:43:23 Reto-Spoerris-MacBook-Pro.local pythonw[4357] <Error>: kCGErrorIllegalArgument: _CGSFindSharedWindow: WID 4659
Wed Oct 21 16:43:23 Reto-Spoerris-MacBook-Pro.local pythonw[4357] <Error>: kCGErrorIllegalArgument: CGSRemoveSurface: Invalid window 0x1233