Major Description
Stateless ajax behaviors are not working in stateless pages in 1.5-RC4.2. I verified it with the stateless demo project of Martin Grigorov (https://github.com/martin-g/wicket-stateless), when changing the dropdown on the start page an exception is thrown (clicking the increment link causes a similar exception):
org.apache.wicket.behavior.InvalidBehaviorIdException: Cannot find behavior with id: 0 on component: [DropDownChoice [Component id = c]]
At first glance the reason may be located in org.apache.wicket.Behaviors.getBehaviorById() which does not create the ID list if missing (getBehaviorsIdList(false) in line 286 instead of getBehaviorsIdList(true)), because this error does not occur when getBehaviorId() was manually called in the page constructor to force creation of the list.