completed constraint checkers for af3.component.

refs 437

org.fortiss.tooling.kernel/trunk/src/org/fortiss/tooling/kernel/extension/base/MultiViolationConstraintCheckerBase.java

@@ -37,7 +37,7 @@ import org.fortiss.tooling.kernel.extension.data.IConstraintViolation;
  * @author hoelzl
  * @author $Author$
  * @version $Rev$
- * @ConQAT.Rating YELLOW Hash: 63108397E80BABBB4828D0094A82C776
+ * @ConQAT.Rating YELLOW Hash: F233654B247B3C3A35A368F7BB909B43
  */
 public abstract class MultiViolationConstraintCheckerBase<T extends EObject, V extends EObject>
 		extends ConstraintCheckerBase<T> {
@@ -47,7 +47,7 @@ public abstract class MultiViolationConstraintCheckerBase<T extends EObject, V e
 	public final List<? extends IConstraintViolation<V>> apply(T modelElement) {
 		List<IConstraintViolation<V>> results = new ArrayList<IConstraintViolation<V>>();
 		collectViolations(modelElement, results);
-		return results;
+		return results.isEmpty() ? null : results;
 	}
 
 	/** Collects the violations in the given result lists. */