a comment about the ElementImpl super class

git-svn-id: https://svn.apache.org/repos/asf/xmlgraphics/fop/trunk@193613 13f79535-47bb-0310-9956-ffa450edef68

src/org/apache/fop/dom/svg/SVGElementImpl.java

 	}
 }
 
-public abstract class SVGElementImpl extends ElementImpl implements GraphicImpl, SVGElement {
+/*
+I want to use
+org.apache.xerces.dom.ElementImpl
+but it causes an null pointer exception in appendChild
+*/
+public abstract class SVGElementImpl extends ElementImpl/*org.apache.xerces.dom.ElementImpl*/ implements GraphicImpl, SVGElement {
 	String idString = "";
 
 	public String getId()