Server console is filled with exceptions when applying ?restartApplication to the url while a dialog is opened in Pages app.

Steps to reproduce:
1. Open Pages App and edit any page
2. Edit page properties to open a modal dialog
3. Enter URL in browser containing the ?restartApplication parameter
4. Admincentral seems to be working, but console is filled with exceptions and warnings.

[INFO] [talledLocalContainer] 2013-06-03 13:27:22,196 WARN info.magnolia.event.SimpleEventBus : Exception caught when dispatching event: null
[INFO] [talledLocalContainer] java.lang.NullPointerException
[INFO] [talledLocalContainer] at info.magnolia.ui.vaadin.magnoliashell.MagnoliaShell.showError(MagnoliaShell.java:139)
[INFO] [talledLocalContainer] at info.magnolia.ui.framework.shell.ShellImpl.messageSent(ShellImpl.java:239)
[INFO] [talledLocalContainer] at info.magnolia.ui.framework.message.MessageEvent.dispatch(MessageEvent.java:56)
[INFO] [talledLocalContainer] at info.magnolia.ui.framework.message.MessageEvent.dispatch(MessageEvent.java:41)
[INFO] [talledLocalContainer] at info.magnolia.event.SimpleEventBus.fireEvent(SimpleEventBus.java:78)
[INFO] [talledLocalContainer] at info.magnolia.ui.framework.message.LocalMessageDispatcher.messageSent(LocalMessageDispatcher.java:57)
[INFO] [talledLocalContainer] at info.magnolia.ui.framework.message.MessagesManagerImpl.sendMessageSentEvent(MessagesManagerImpl.java:180)
[INFO] [talledLocalContainer] at info.magnolia.ui.framework.message.MessagesManagerImpl.sendLocalMessage(MessagesManagerImpl.java:112)
[INFO] [talledLocalContainer] at info.magnolia.ui.admincentral.AdmincentralErrorHandler.error(AdmincentralErrorHandler.java:71)
[INFO] [talledLocalContainer] at info.magnolia.ui.admincentral.AdmincentralUI.detach(AdmincentralUI.java:119)
[INFO] [talledLocalContainer] at com.vaadin.ui.UI.setSession(UI.java:344)
[INFO] [talledLocalContainer] at com.vaadin.server.VaadinSession.removeUI(VaadinSession.java:626)
[INFO] [talledLocalContainer] at com.vaadin.server.VaadinService.fireSessionDestroy(VaadinService.java:340)
[INFO] [talledLocalContainer] at com.vaadin.server.VaadinSession.valueUnbound(VaadinSession.java:181)
[INFO] [talledLocalContainer] at org.mortbay.jetty.servlet.AbstractSessionManager$Session.unbindValue(AbstractSessionManager.java:1133)
[INFO] [talledLocalContainer] at org.mortbay.jetty.servlet.AbstractSessionManager$Session.removeAttribute(AbstractSessionManager.java:1027)
[INFO] [talledLocalContainer] at org.mortbay.jetty.servlet.AbstractSessionManager$Session.setAttribute(AbstractSessionManager.java:1053)

[WARNING] [talledLocalContainer] WARNING: Unregistered Label (115) that was already unregistered.
[WARNING] [talledLocalContainer] Jun 3, 2013 1:27:22 PM com.vaadin.ui.ConnectorTracker unregisterConnector