Connector title disappears when (re-)opening a cluster

affected: vis-network.min.js (4.21.0), not affected: vis-network.min.js (4.20.1)

Please see the series of screenshots. So far, we haven't created an isolated code snippet provoking the error - because you might have a suspiction knowing what has been changed from 4.20.1 to 4.21.0. But we could invest some time, if you have no idea and cannot reproduce it with your testcases.