"Add folder of type.." broken

When trying to create a new folder of type, a dialog opens with folder name and type dropdown.
After entering good input and hitting OK, this shows: java.lang.IllegalArgumentException: No folder type selected.

Full stacktrace:

26.06.2008 14:13:22 ERROR [org.hippoecm.frontend.dialog.AbstractDialog$1.onClick
():58] java.lang.IllegalArgumentException: No folder type selected.
java.lang.IllegalArgumentException: No folder type selected.
at org.hippoecm.frontend.plugins.standardworkflow.dialogs.ExtendedFolder
Dialog.execute(ExtendedFolderDialog.java:103)
at org.hippoecm.frontend.dialog.AbstractWorkflowDialog.ok(AbstractWorkfl
owDialog.java:108)
at org.hippoecm.frontend.dialog.AbstractDialog$1.onClick(AbstractDialog.
java:54)
at org.apache.wicket.ajax.markup.html.AjaxLink$1.onEvent(AjaxLink.java:6
5)
at org.apache.wicket.ajax.AjaxEventBehavior.respond(AjaxEventBehavior.ja
va:163)
at org.apache.wicket.ajax.AbstractDefaultAjaxBehavior.onRequest(Abstract
DefaultAjaxBehavior.java:293)
at org.apache.wicket.request.target.component.listener.BehaviorRequestTa
rget.processEvents(BehaviorRequestTarget.java:100)
at org.apache.wicket.request.AbstractRequestCycleProcessor.processEvents
(AbstractRequestCycleProcessor.java:91)
at org.apache.wicket.RequestCycle.processEventsAndRespond(RequestCycle.j
ava:1171)
at org.apache.wicket.RequestCycle.step(RequestCycle.java:1248)
at org.apache.wicket.RequestCycle.steps(RequestCycle.java:1349)
at org.apache.wicket.RequestCycle.request(RequestCycle.java:493)
at org.apache.wicket.protocol.http.WicketFilter.doGet(WicketFilter.java:
387)
at org.apache.wicket.protocol.http.WicketFilter.doFilter(WicketFilter.ja
va:199)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(Servlet
Handler.java:1084)
at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:3
60)
at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.jav
a:216)
at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:1
81)
at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:7
26)
at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:405)

at org.mortbay.jetty.handler.ContextHandlerCollection.handle(ContextHand
lerCollection.java:206)
at org.mortbay.jetty.handler.HandlerCollection.handle(HandlerCollection.
java:114)
at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:1
52)
at org.mortbay.jetty.Server.handle(Server.java:324)
at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:50
5)
at org.mortbay.jetty.HttpConnection$RequestHandler.headerComplete(HttpCo
nnection.java:829)
at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:514)
at org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:211)
at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:380)
at org.mortbay.io.nio.SelectChannelEndPoint.run(SelectChannelEndPoint.ja
va:395)
at org.mortbay.thread.QueuedThreadPool$PoolThread.run(QueuedThreadPool.j
ava:488)