bui-agent failed with 0.4.3

Hello Benjamin,

I have noticed when trying to upgrade to 0.4.3 I got this error with bui-agent:

/usr/local/bin/bui-agent -v -c /etc/burp/buiagent.cfg                                                  [2016-12-30 13:53:10,225] ERROR in agent.__init__: Traceback (most recent call last):
  File "/usr/local/lib/python2.7/dist-packages/burpui/agent.py", line 60, in __init__
    self.backend = Client(conf=conf)
  File "/usr/local/lib/python2.7/dist-packages/burpui/misc/backend/burp2.py", line 235, in __init__
    if not self.app.config['BUI_CLI']:
AttributeError: 'NoneType' object has no attribute 'config'


Failed loading backend for Burp version 2: 'NoneType' object has no attribute 'config'

I have no hurry with it because I can use 0.4.2 and it works fine.

Thanks a lot for fixing bugs on burpui, sorry to be reporting a new one... (have upgraded to 0.4.3 burpui central and keep 0.4.2 on bui-agent with no issues)

Have a happy new year!!