If connections are idle past MySQL's wait_timeout setting, then exceptions will occur the next time the user tries to load a page on the Administrator that uses MyBatis.
Usually the error is harmless and a new connection will be created the next time a request is made. If for some reason someone REALLY needs a workaround right now, the answer is to run the following code from a deploy script or something each time the server is started. Ideally the "setPoolPingConnectionsNotUsedFor" value should be slightly less than the "wait_timeout" value that's set in MySQL. Note that the "wait_timeout" value is in seconds while the "setPoolPingConnectionsNotUsedFor" value is in milliseconds.