DepthFirst*Traversal cannot handle a default value other than null

Signed-off-by: Florian Thienel <florian@thienel.org>
diff --git a/org.eclipse.vex.core/src/org/eclipse/vex/core/internal/dom/DepthFirstNodeTraversal.java b/org.eclipse.vex.core/src/org/eclipse/vex/core/internal/dom/DepthFirstNodeTraversal.java
index 5e47147..97ab9df 100644
--- a/org.eclipse.vex.core/src/org/eclipse/vex/core/internal/dom/DepthFirstNodeTraversal.java
+++ b/org.eclipse.vex.core/src/org/eclipse/vex/core/internal/dom/DepthFirstNodeTraversal.java
@@ -20,11 +20,7 @@
 public class DepthFirstNodeTraversal<T> extends BaseNodeVisitorWithResult<T> {
 
 	public DepthFirstNodeTraversal() {
-		this(null);
-	}
-
-	public DepthFirstNodeTraversal(final T defaultValue) {
-		super(defaultValue);
+		super(null);
 	}
 
 	@Override