[BACKPORT] Channel Manager perspective is not visible and logs ERROR when the site is not running

When the site is not running and the CMS is accessed, the channel manager icon is not visible (see screenshot) and the following ERROR logged:

[INFO] [talledLocalContainer] 22.03.2012 14:44:48 ERROR [org.hippoecm.frontend.plugin.impl.PluginFactory.createPlugin():90] org.apache.cxf.jaxrs.client.ServerWebApplicationException:
[INFO] [talledLocalContainer] java.lang.reflect.InvocationTargetException
[INFO] [talledLocalContainer] at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
[INFO] [talledLocalContainer] at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
[INFO] [talledLocalContainer] at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
[INFO] [talledLocalContainer] at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
[INFO] [talledLocalContainer] at org.hippoecm.frontend.plugin.impl.PluginFactory.createPlugin(PluginFactory.java:72)
[INFO] [talledLocalContainer] at org.hippoecm.frontend.plugin.impl.PluginManager.start(PluginManager.java:87)
[INFO] [talledLocalContainer] at org.hippoecm.frontend.plugin.impl.PluginContext.start(PluginContext.java:320)
[INFO] [talledLocalContainer] at org.hippoecm.frontend.plugin.impl.ClusterControl.start(ClusterControl.java:126)
[INFO] [talledLocalContainer] at org.hippoecm.frontend.PluginPage.<init>(PluginPage.java:117)
[INFO] [talledLocalContainer] at org.hippoecm.frontend.PluginPage.<init>(PluginPage.java:70)
[INFO] [talledLocalContainer] at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
[INFO] [talledLocalContainer] at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
[INFO] [talledLocalContainer] at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
[INFO] [talledLocalContainer] at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
[INFO] [talledLocalContainer] at org.apache.wicket.session.DefaultPageFactory.createPage(DefaultPageFactory.java:192)
[INFO] [talledLocalContainer] at org.apache.wicket.session.DefaultPageFactory.newPage(DefaultPageFactory.java:57)
[INFO] [talledLocalContainer] at org.apache.wicket.request.target.component.BookmarkablePageRequestTarget.newPage(BookmarkablePageRequestTarget.java:298)
[INFO] [talledLocalContainer] at org.apache.wicket.request.target.component.BookmarkablePageRequestTarget.getPage(BookmarkablePageRequestTarget.java:320)
[INFO] [talledLocalContainer] at org.apache.wicket.request.target.component.BookmarkablePageRequestTarget.processEvents(BookmarkablePageRequestTarget.java:234)
[INFO] [talledLocalContainer] at org.apache.wicket.request.AbstractRequestCycleProcessor.processEvents(AbstractRequestCycleProcessor.java:92)
[INFO] [talledLocalContainer] at org.hippoecm.frontend.PluginRequestCycleProcessor.processEvents(PluginRequestCycleProcessor.java:95)
[INFO] [talledLocalContainer] at org.apache.wicket.RequestCycle.processEventsAndRespond(RequestCycle.java:1252)
[INFO] [talledLocalContainer] at org.apache.wicket.RequestCycle.step(RequestCycle.java:1331)
[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:54)
[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: Status : 404
[INFO] [talledLocalContainer] Headers :
[INFO] [talledLocalContainer] Date : Thu, 22 Mar 2012 13:44:48 GMT
[INFO] [talledLocalContainer] Content-Length : 0
[INFO] [talledLocalContainer] Server : Apache-Coyote/1.1
[INFO] [talledLocalContainer]
[INFO] [talledLocalContainer] at org.apache.cxf.jaxrs.client.ClientProxyImpl.checkResponse(ClientProxyImpl.java:233)
[INFO] [talledLocalContainer] at org.apache.cxf.jaxrs.client.ClientProxyImpl.handleResponse(ClientProxyImpl.java:453)
[INFO] [talledLocalContainer] at org.apache.cxf.jaxrs.client.ClientProxyImpl.doChainedInvocation(ClientProxyImpl.java:445)
[INFO] [talledLocalContainer] at org.apache.cxf.jaxrs.client.ClientProxyImpl.invoke(ClientProxyImpl.java:177)
[INFO] [talledLocalContainer] at $Proxy47.getBlueprints(Unknown Source)
[INFO] [talledLocalContainer] at org.onehippo.cms7.channelmanager.channels.BlueprintStore.getBlueprints(BlueprintStore.java:103)
[INFO] [talledLocalContainer] at org.onehippo.cms7.channelmanager.channels.BlueprintStore.getTotal(BlueprintStore.java:58)
[INFO] [talledLocalContainer] at org.onehippo.cms7.channelmanager.channels.BlueprintStore.isEmpty(BlueprintStore.java:64)
[INFO] [talledLocalContainer] at org.onehippo.cms7.channelmanager.RootPanel.<init>(RootPanel.java:107)
[INFO] [talledLocalContainer] at org.onehippo.cms7.channelmanager.ChannelManagerPerspective.<init>(ChannelManagerPerspective.java:54)
[INFO] [talledLocalContainer] ... 46 more

Steps to reproduce:

1. start CMS and site locally:
mvn -P cargo.run

2. stop the site:
cd site
mvn cargo:undeploy

3. access http://localhost:8080/cms and login as admin

Expected behaviour: no error is logged; the channel manager icon is shown, but no channels or blueprints are available. The UI shows an error message describing the situation.
Actual behaviour: the error described above is logged, and the channel manager icon is not visible