Re-enable toString() for the properties which wrap another object.

git-svn-id: https://svn.apache.org/repos/asf/xmlgraphics/fop/trunk@197316 13f79535-47bb-0310-9956-ffa450edef68

src/java/org/apache/fop/fo/properties/Property.java

@@ -212,6 +212,10 @@ public class Property {
      * for debugging.
      */
     public String toString() {
-        return getString();
+        Object obj = getObject();
+        if (obj != this) {
+            return obj.toString();
+        }
+        return null;
     }
 }