OO-1882: in assessment mode editor, highlight the right field if course...

OO-1882: in assessment mode editor, highlight the right field if course elements options are selected but not the course elements

src/main/java/org/olat/course/assessment/ui/AssessmentModeEditController.java

@@ -458,7 +458,7 @@ public class AssessmentModeEditController extends FormBasicController {
 		courseElementsRestrictionEl.clearError();
 		if(courseElementsRestrictionEl.isAtLeastSelected(1)) {
 			if(elementKeys.isEmpty()) {
-				endEl.setErrorKey("form.legende.mandatory", null);
+				courseElementsRestrictionEl.setErrorKey("form.legende.mandatory", null);
 				allOk &= false;
 			}
 		}