Update-QlikDataconnection remove credentials

[cuthulino]

It is not possible to remove the credentials of a dataconnection.
With New-QlikDataconnection you can pass nothing or $null and the credentials will be empty.
Passing $null to the Update-QlikDataconnection function returns no error but the old credentials persist.
Passing a empty credential object [System.Management.Automation.PSCredential]::Empty returns an error because the method GetNetworkCredential() can not be called on an empty credential object.

There should be a possibility to clear the credentials of a dataconnection (like sending Null value)