support intersecting

git-svn-id: https://svn.code.sf.net/p/jode/code/trunk@917 379699f6-c40d-0410-875b-85095c16579e

jode/jode/type/NullType.java

@@ -78,6 +78,8 @@ public class NullType extends ReferenceType {
      * @return the intersection, or tError, if a type conflict happens.
      */
     public Type intersection(Type type) {
-	throw new AssertError("NULL.intersection");
+	if (type == this)
+	    return type;
+	return tError;
     }
 }