We have configured "Server Information (proxyconfiguration)" with https but without port number.
The result is following Link with -1:
As to the setting in SC/Admin/Config > /HTTPS=Yes and > /Server Information > Port Number is left empty.
Which then leads to a URL being created with port -1.
No info is to be found where it is stated that the port number can be left empty.
Nor that this field is mandatory.
The workaround then is: set the port number to a 'dummy' value (443).