HTTP status 500 when clicking multiple times on the OK button at image upload (Flash off)

When clicking multiple times on the OK button at image upload (flash disabled) you get a HTTP 500 error

Reproduction path

• Build and run project with archetype (archetype version 1.05.07, Hippo CMS version 7.7.5)
  disable flash image uploader (add boolean property 'fileupload.flashEnabled' with value 'false' under /hippo:configuration/hippo:workflows/gallery/image-gallery/frontend:renderer)
• Go to the Images
• Upload an image to a folder you like
• Click fast on OK until HTTP status 500 appears

NOTE:
I don't know why, but sometimes nothing special happens. Usually when I try it over and over again. Stopping and starting the project will make the problem appears again.

The URL of the HTTP status 500 is http://localhost:8080/cms/?wicket:interface=:1:dialog:content:form::IFormSubmitListener::

The message logged:
[INFO] [talledLocalContainer] 23.08.2012 10:17:08 ERROR [org.apache.wicket.RequestCycle.logRuntimeException():1531] org.apache.wicket.WicketRuntimeException: component dialog:content:form not found on page org.hippoecm.frontend.PluginPage[id = 1], listener interface = [RequestListenerInterface name=IFormSubmitListener, method=public abstract void org.apache.wicket.markup.html.form.IFormSubmitListener.onFormSubmitted()]
[INFO] [talledLocalContainer] org.apache.wicket.protocol.http.request.InvalidUrlException: org.apache.wicket.WicketRuntimeException: component dialog:content:form not found on page org.hippoecm.frontend.PluginPage[id = 1], listener interface = [RequestListenerInterface name=IFormSubmitListener, method=public abstract void org.apache.wicket.markup.html.form.IFormSubmitListener.onFormSubmitted()]
[INFO] [talledLocalContainer] at org.apache.wicket.protocol.http.WebRequestCycleProcessor.resolve(WebRequestCycleProcessor.java:262)
[INFO] [talledLocalContainer] at org.apache.wicket.RequestCycle.step(RequestCycle.java:1312)
[INFO] [talledLocalContainer] at org.apache.wicket.RequestCycle.steps(RequestCycle.java:1438)
[INFO] [talledLocalContainer] at org.apache.wicket.RequestCycle.request(RequestCycle.java:546)
[INFO] [talledLocalContainer] at org.apache.wicket.protocol.http.WicketFilter.doGet(WicketFilter.java:486)
[INFO] [talledLocalContainer] at org.apache.wicket.protocol.http.WicketFilter.doFilter(WicketFilter.java:319)
[INFO] [talledLocalContainer] at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
[INFO] [talledLocalContainer] at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
[INFO] [talledLocalContainer] at org.hippoecm.frontend.ResourceRewriteFilter.doFilter(ResourceRewriteFilter.java:129)
[INFO] [talledLocalContainer] at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
[INFO] [talledLocalContainer] at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
[INFO] [talledLocalContainer] at org.hippoecm.frontend.plugins.login.ConcurrentLoginFilter.doFilter(ConcurrentLoginFilter.java:56)
[INFO] [talledLocalContainer] at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
[INFO] [talledLocalContainer] at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
[INFO] [talledLocalContainer] at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
[INFO] [talledLocalContainer] at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
[INFO] [talledLocalContainer] at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
[INFO] [talledLocalContainer] at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
[INFO] [talledLocalContainer] at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:589)
[INFO] [talledLocalContainer] at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
[INFO] [talledLocalContainer] at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:291)
[INFO] [talledLocalContainer] at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:859)
[INFO] [talledLocalContainer] at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:602)
[INFO] [talledLocalContainer] at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489)
[INFO] [talledLocalContainer] at java.lang.Thread.run(Thread.java:662)
[INFO] [talledLocalContainer] Caused by: org.apache.wicket.WicketRuntimeException: component dialog:content:form not found on page org.hippoecm.frontend.PluginPage[id = 1], listener interface = [RequestListenerInterface name=IFormSubmitListener, method=public abstract void org.apache.wicket.markup.html.form.IFormSubmitListener.onFormSubmitted()]
[INFO] [talledLocalContainer] at org.apache.wicket.request.AbstractRequestCycleProcessor.resolveListenerInterfaceTarget(AbstractRequestCycleProcessor.java:427)
[INFO] [talledLocalContainer] at org.apache.wicket.request.AbstractRequestCycleProcessor.resolveRenderedPage(AbstractRequestCycleProcessor.java:472)
[INFO] [talledLocalContainer] at org.apache.wicket.protocol.http.WebRequestCycleProcessor.resolve(WebRequestCycleProcessor.java:144)
[INFO] [talledLocalContainer] ... 24 more