The getResource() method is being called for a mounted ResourceReference even when the url does not match. So far it seems to only happen when some wicket Ajax is included in the page. To get around the problem, I've added a check on my ResourceReference that looks for the mounted name in the request url but it seems like the mounting should handle that.
To reproduce the error:
1. Call mountResource("uploadedfiles", MyResourceReference.class);
2. Add an AjaxFallbackLink to a page
3. In MyResourceReference getResource() method return null;
4. Run the application and open the page with an AjaxFallbackLink and you will get
The class org.apache.wicket.request.mapper.ResourceMap calls the getResource() (line 167) method even though the url does not match the mounted name.