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

sometimes I can open commit viewer from a selected commit in History View but most often I hit the following exception:

org.eclipse.core.commands.ExecutionException: Could not get the repository from the history view
	at org.eclipse.egit.ui.internal.history.command.AbstractHistoryCommandHandler.getRepository(AbstractHistoryCommandHandler.java:100)
	at org.eclipse.egit.ui.internal.history.command.OpenInCommitViewerHandler.execute(OpenInCommitViewerHandler.java:31)
	at org.eclipse.ui.internal.handlers.HandlerProxy.execute(HandlerProxy.java:293)
	at org.eclipse.core.commands.Command.executeWithChecks(Command.java:476)
	at org.eclipse.core.commands.ParameterizedCommand.executeWithChecks(ParameterizedCommand.java:508)
	at org.eclipse.ui.internal.handlers.HandlerService.executeCommand(HandlerService.java:169)
	at org.eclipse.ui.internal.handlers.SlaveHandlerService.executeCommand(SlaveHandlerService.java:241)
	at org.eclipse.ui.internal.handlers.SlaveHandlerService.executeCommand(SlaveHandlerService.java:241)
	at org.eclipse.ui.internal.handlers.SlaveHandlerService.executeCommand(SlaveHandlerService.java:241)
	at org.eclipse.ui.menus.CommandContributionItem.handleWidgetSelection(CommandContributionItem.java:829)
	at org.eclipse.ui.menus.CommandContributionItem.access$19(CommandContributionItem.java:815)
	at org.eclipse.ui.menus.CommandContributionItem$5.handleEvent(CommandContributionItem.java:805)
	at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:84)
	at org.eclipse.swt.widgets.Display.sendEvent(Display.java:4128)
	at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1457)
	at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1480)