[core] sync_groups_on_login doesn't work with NT Domain

When configuring Ldap with "nt_domain" and "sync_groups_on_login", hue goes through this piece of code in ldap_access.py:

def get_connection_from_server(server=None):
if server:
return get_connection(desktop.conf.LDAP.LDAP_SERVERS.get()[server], search_bind_authentication=desktop.conf.LDAP.SEARCH_BIND_AUTHENTICATION.get())
else:
return get_connection(desktop.conf.LDAP, search_bind_authentication=desktop.conf.LDAP.SEARCH_BIND_AUTHENTICATION.get())

However, since we aren't specifying LDAP_SERVERS, the return within "if server" throws a 500 error.