File edit get_neighbourhood() calling error is resolved

**Error Reference:**

Traceback (most recent call last):

  File "/home/glab/gstudio_metastudio/local/lib/python2.7/site-packages/django/core/handlers/base.py", line 112, in get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)

  File "./gnowsys_ndf/ndf/views/file.py", line 1060, in file_edit
    file_node.get_neighbourhood(file_node.member_of)

AttributeError: 'NoneType' object has no attribute 'get_neighbourhood'