Crash when disconnecting

DEBUG:mainwindow:refresh:Refresh started
DEBUG:network:discover_network:End of network discovery
DEBUG:__init__:requests_get:Request : http://urodelus.ddns.net:9201/wot/members
DEBUG:__init__:requests_get:Request : http://ucoin.inso.ovh:80/wot/members
DEBUG:main:async_exception_handler:Exception handler executing
ERROR:main:async_exception_handler:Task exception was never retrieved
future: <Task finished coro=<refresh() done, defined at /Users/quentin/dev/sakia/src/sakia/gui/community_tile.py:58> exception=AttributeError("'NoneType' object has no attribute 'amount'",)>
Traceback (most recent call last):
  File "/Users/quentin/.pyenv/versions/3.4.3/Python.framework/Versions/3.4/lib/python3.4/asyncio/tasks.py", line 236, in _step
    result = coro.send(value)
  File "/Users/quentin/dev/sakia/src/sakia/gui/community_tile.py", line 66, in refresh
    amount = yield from self.app.current_account.amount(self.community)
AttributeError: 'NoneType' object has no attribute 'amount'