ShowBase.oobe() call crashes: AttributeError: 'NoneType' has no attribute 'findAllMatches'

[Niels Huylebroeck]

Ubuntu Lucid - 64bit
Panda3D 1.8.0 official

When calling oobeCull() on ShowBase without any arguments I get this error, when I manually pass my camera object (which is the regular ShowBase.cam) it seems to work.

Traceback (most recent call last):
  File "/usr/share/panda3d/direct/showbase/EventManager.py", line 61, in eventLoopTask
    self.doEvents()
  File "/usr/share/panda3d/direct/showbase/EventManager.py", line 55, in doEvents
    processFunc(self.eventQueue.dequeueEvent())
  File "/usr/share/panda3d/direct/showbase/EventManager.py", line 124, in processEvent
    messenger.send(eventName)
  File "/usr/share/panda3d/direct/showbase/Messenger.py", line 397, in send
    self.__dispatch(acceptorDict, event, sentArgs, foundWatch)
  File "/usr/share/panda3d/direct/showbase/Messenger.py", line 482, in __dispatch
    method (*(extraArgs + sentArgs))
  File "/usr/share/panda3d/direct/showbase/ShowBase.py", line 2338, in oobeCull
    for c in cam.findAllMatches('**/+Camera'):
AttributeError: 'NoneType' object has no attribute 'findAllMatches'
:task(error): Exception occurred in PythonTask eventManager
Traceback (most recent call last):
  File "run.py", line 5, in <module>
    merc.main.app.run()
  File "/usr/share/panda3d/direct/showbase/ShowBase.py", line 2910, in run
    self.taskMgr.run()
  File "/usr/share/panda3d/direct/task/Task.py", line 502, in run
    self.step()
  File "/usr/share/panda3d/direct/task/Task.py", line 460, in step
    self.mgr.poll()
  File "/usr/share/panda3d/direct/showbase/EventManager.py", line 61, in eventLoopTask
    self.doEvents()
  File "/usr/share/panda3d/direct/showbase/EventManager.py", line 55, in doEvents
    processFunc(self.eventQueue.dequeueEvent())
  File "/usr/share/panda3d/direct/showbase/EventManager.py", line 124, in processEvent
    messenger.send(eventName)
  File "/usr/share/panda3d/direct/showbase/Messenger.py", line 397, in send
    self.__dispatch(acceptorDict, event, sentArgs, foundWatch)
  File "/usr/share/panda3d/direct/showbase/Messenger.py", line 482, in __dispatch
    method (*(extraArgs + sentArgs))
  File "/usr/share/panda3d/direct/showbase/ShowBase.py", line 2338, in oobeCull
    for c in cam.findAllMatches('**/+Camera'):
AttributeError: 'NoneType' object has no attribute 'findAllMatches'