Examples from "Form Optional / Required" section of the form reference: convert whitespace only string value to {absent} with ctrl.emptyisnull=true

Field String Optional Empty Is Null(Optional)Optional string field with ctrl.emptyisnull=true can submit whitespace only value but converts them to the {absent} (null) value. If there are also characters, whitespace is not collapsed.

Field String Required Empty Is Null *Required string field with ctrl.emptyisnull=true can submit whitespace only value but converts them to the {absent} (null) value so that validation fails. If there are also characters, whitespace is not collapsed.