Store property type information from most specific class instead of m…

…ost generic class

JSONModel/JSONModel/JSONModel.m

@@ -670,7 +670,7 @@ -(void)__inspectProperties
             }
 
             //add the property object to the temp index
-            if (p) {
+            if (p && ![propertyIndex objectForKey:p.name]) {
                 [propertyIndex setValue:p forKey:p.name];
             }
         }