Added new warning message to be used when the variable that was added has no valid values

GCP-8596

Reviewer: Cyrus Casada
Added a new message variable in the globals.html to be use when showing an error message for variable that is added that has no valid value

GCP-8596

Reviewer: Cyrus Casada
Added checking if the variable being added is a categorical variable and checks if its has possible values or not, if there is no possible values, we would show a warning message to the user

GCP-8596

Reviewer: Cyrus Casada