Call OnMenuPress(nil) when hitting esc in a menu

OnMenuPress can already deal with the selected item being nil, so this allows us
to add common code to it that is run when cancelling the menu.

pkg/gui/controllers/menu_controller.go

@@ -78,8 +78,7 @@ func (self *MenuController) close() error {
 		return nil
 	}
 
-	self.c.Context().Pop()
-	return nil
+	return self.context().OnMenuPress(nil)
 }
 
 func (self *MenuController) context() *context.MenuContext {