For example, a customer has accidentally created an agent with a space in the host field. This should not have validated, and even if it gets through it should not prevent the agent from being listed on the agents page (which is does as the malformedurlexception prevents addition of the agent to the slaves list). The latter art is trick as we need to know not to try touching this agent if it has no slaveservice - which we can't create when the host is invalid.