Fixes errors that can occur during remodelling after removing of a component, such as:

  AttributeError: Unable to determine parent at <Instance at server-df90c26d-3295-4413-a6b7-68283ccde6f7> ('NoneType' object has no attribute 'primaryAq') while getting device for <Instance at server-df90c26d-3295-4413-a6b7-68283ccde6f7>
Merge pull request #26 from zenoss/feature/device_exception

Fixes errors that can occur during remodelling after removing of a compo...