Logon with negative heartbeat interval (HeartBtInt) should be rejected

When logging on with a negative heartbeat interval, the Logon is accepted but then the connection is terminated immediately due to a Heartbeat timeout ("Disconnecting: Timed out waiting for heartbeat").

I would propose to reject the Logon in case of a negative HeartBtInt setting.

Maybe the check for the negative interval should be done somewhere at the beginning inside Session.nextLogon(). Is this a valid place for this check? Any comments?