fix: disappearing info message after mandatory property assignment

SVN: 15265

openbis/source/java/ch/systemsx/cisd/openbis/generic/client/web/client/application/ui/property_type/PropertyTypeAssignmentForm.java

@@ -254,6 +254,7 @@ public final class PropertyTypeAssignmentForm extends LayoutContainer implements
         {
             mandatoryCheckbox = new CheckBoxField(viewContext.getMessage(Dict.MANDATORY), false);
             mandatoryCheckbox.setId(createChildId(MANDATORY_CHECKBOX_ID_SUFFIX));
+            mandatoryCheckbox.setFireChangeEventOnSetValue(false);
             mandatoryCheckbox.setValue(false);
             mandatoryCheckbox.addListener(Events.Change, new InfoBoxResetListener(infoBox));
         }