allow for null transformation results

Signed-off-by: Juergen Albert <j.albert@data-in-motion.biz>

org.gecko.qvt.osgi/src/org/gecko/qvt/osgi/component/QVTModelTransformator.java

@@ -162,7 +162,7 @@ public <T extends EObject> T doTransformation(List<? extends EObject> inObjects)
 		if (outObjects.size() > 0) {
 			return (T) outObjects.get(0);
 		}
-		throw new IllegalStateException("Transformation failed with no result object");
+		return null;
 	}
 
 	/*