allow empty servers (Fixes: #3874)

Florian Schaal

2016-05-04 cc08f2c13f7155d6f3fb11afa7661aaec676858a

1
ALTER TABLE  `sys_session` CHANGE  `session_id`  `session_id` VARCHAR( 64 ) CHARACTER SET latin1 COLLATE latin1_swedish_ci NOT NULL;