[ADF-4797] - fix null value for display text when the field it's not visible (#4987)

* fix reset display text value when it's not visible

* change invalid unit test

* change unit test

* use alpha to test

lib/core/form/services/widget-visibility.service.ts

@@ -48,9 +48,6 @@ export class WidgetVisibilityService {
 
     refreshEntityVisibility(element: FormFieldModel | TabModel) {
         const visible = this.evaluateVisibility(element.form, element.visibilityCondition);
-        if (!visible && element instanceof FormFieldModel) {
-            element.value = null;
-        }
         element.isVisible = visible;
     }