Division by Zero error in member statistics

[Kurocon]

When a date in the future (or in the past where no member data exists) is selected, a ZeroDivisionError is thrown on the member statistics page.

amelie/amelie/members/views.py

Line 128 in 6f36f1e

percent_active_members = '{0:.2f}'.format((active_members_count*100.0)/members_count)

ZeroDivisionError:float division by zero
File "django/core/handlers/exception.py", line 47, in inner
     response = get_response(request)
File "django/core/handlers/base.py", line 181, in _get_response
     response = wrapped_callback(request, *callback_args, **callback_kwargs)
File "amelie/tools/decorators.py", line 33, in _do_test_request
     return view_func(request, *args, **kwargs)
File "amelie/members/views.py", line 128, in statistics
     percent_active_members = '{0:.2f}'.format((active_members_count*100.0)/members_count)