added null check for observed object

org.fortiss.tooling.kernel.ui/trunk/src/org/fortiss/tooling/kernel/ui/internal/databinding/EObjectObservableValue.java

@@ -70,6 +70,12 @@ public class EObjectObservableValue extends AbstractObservableValue {
 	/** Constructor. */
 	public EObjectObservableValue(Realm realm, EObject eObject, EStructuralFeature structuralFeature) {
 		super(realm);
+
+		if(eObject == null)
+			throw new NullPointerException();
+		if(structuralFeature == null)
+			throw new NullPointerException();
+
 		this.eObject = eObject;
 		this.structuralFeature = structuralFeature;