[oozie] Prevent 500 error when listing a workflow which coordinator is none

  File "/usr/local/hue/build/env/lib/python2.7/site-packages/Django-1.6.10-py2.7.egg/django/core/handlers/base.py", line 112, in get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/usr/local/hue/build/env/lib/python2.7/site-packages/Django-1.6.10-py2.7.egg/django/db/transaction.py", line 371, in inner
    return func(*args, **kwargs)
  File "/usr/local/hue/apps/oozie/src/oozie/views/dashboard.py", line 166, in decorate
    return view_func(request, *args, **kwargs)
  File "/usr/local/hue/apps/oozie/src/oozie/views/dashboard.py", line 385, in list_oozie_workflow
    'hue_coord': hue_coord,
UnboundLocalError: local variable 'hue_coord' referenced before assignment