0003243: AS400 default catalog must be null and not empty string or

readTables on the meta data will never return results

symmetric-jdbc/src/main/java/org/jumpmind/db/platform/db2/Db2As400DatabasePlatform.java

@@ -35,5 +35,11 @@ public String getDefaultSchema() {
         }
         return defaultSchema;
     }
+
+    @Override
+    public String getDefaultCatalog() {
+    		// This must return null for AS400, an empty string will return no match on readTable meta data.    	
+    		return null;
+    }
 
 }