Patch Set 2: I would prefer that you didn't submit this

- rebased to current master

- on egit repository I opened the history view
   then I clicked the compare mode toggle button so that it's down
   then I clicked the show all branches toggle button
   this throws an error :

!MESSAGE Problems occurred when invoking code from plug-in: "org.eclipse.ui.workbench".
!STACK 0
org.eclipse.swt.SWTException: Widget is disposed
	at org.eclipse.swt.SWT.error(SWT.java:4083)
	at org.eclipse.swt.SWT.error(SWT.java:3998)
	at org.eclipse.swt.SWT.error(SWT.java:3969)
	at org.eclipse.swt.widgets.Widget.error(Widget.java:715)
	at org.eclipse.swt.widgets.Widget.checkWidget(Widget.java:531)
	at org.eclipse.swt.widgets.Control.getParent(Control.java:1615)
	at org.eclipse.egit.ui.internal.history.GitHistoryPage.setErrorMessage(GitHistoryPage.java:1234)
	at org.eclipse.egit.ui.internal.history.GitHistoryPage.inputSet(GitHistoryPage.java:1003)
	at org.eclipse.egit.ui.internal.history.GitHistoryPage.refresh(GitHistoryPage.java:975)
	at org.eclipse.egit.ui.internal.history.GitHistoryPage$3.apply(GitHistoryPage.java:383)
	at org.eclipse.egit.ui.internal.history.GitHistoryPage$BooleanPrefAction.propertyChange(GitHistoryPage.java:1492)
	at org.eclipse.ui.preferences.ScopedPreferenceStore$3.run(ScopedPreferenceStore.java:375)
	at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
	at org.eclipse.ui.preferences.ScopedPreferenceStore.firePropertyChangeEvent(ScopedPreferenceStore.java:372)
	at org.eclipse.ui.preferences.ScopedPreferenceStore.setValue(ScopedPreferenceStore.java:813)
	at org.eclipse.egit.ui.internal.history.GitHistoryPage$BooleanPrefAction.run(GitHistoryPage.java:1476)
	at org.eclipse.jface.action.Action.runWithEvent(Action.java:498)
	at org.eclipse.jface.action.ActionContributionItem.handleWidgetSelection(ActionContributionItem.java:584)
	at org.eclipse.jface.action.ActionContributionItem.access$2(ActionContributionItem.java:501)
	at org.eclipse.jface.action.ActionContributionItem$6.handleEvent(ActionContributionItem.java:452)
	at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:84)
	at org.eclipse.swt.widgets.Display.sendEvent(Display.java:3776)
	at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1367)
	at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1390)
	at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1375)
	at org.eclipse.swt.widgets.Widget.notifyListeners(Widget.java:1187)
	at org.eclipse.swt.widgets.Display.runDeferredEvents(Display.java:3622)
	at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3277)
	at org.eclipse.ui.internal.Workbench.runEventLoop(Workbench.java:2629)
	at org.eclipse.ui.internal.Workbench.runUI(Workbench.java:2593)
	at org.eclipse.ui.internal.Workbench.access$4(Workbench.java:2427)
	at org.eclipse.ui.internal.Workbench$7.run(Workbench.java:670)
	at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:332)
	at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:663)
	at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:149)
	at org.eclipse.ui.internal.ide.application.IDEApplication.start(IDEApplication.java:115)
	at org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:196)
	at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:110)
	at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:79)
	at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:369)
	at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:179)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
	at java.lang.reflect.Method.invoke(Method.java:597)
	at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:619)
	at org.eclipse.equinox.launcher.Main.basicRun(Main.java:574)
	at org.eclipse.equinox.launcher.Main.run(Main.java:1407)
	at org.eclipse.equinox.launcher.Main.main(Main.java:1383)