Do not init Menu lazily, otherwise empty menus would be invalid.

atom/browser/api/lib/menu.coffee

@@ -26,18 +26,7 @@ generateGroupId = (items, pos) ->
 Menu = bindings.Menu
 Menu::__proto__ = EventEmitter.prototype
 
-Menu::popup = (window) ->
+Menu::_init = ->
-  throw new TypeError('Invalid window') unless window?.constructor is BrowserWindow
-  @_popup window
-
-Menu::append = (item) ->
-  @insert @getItemCount(), item
-
-Menu::insert = (pos, item) ->
-  throw new TypeError('Invalid item') unless item?.constructor is MenuItem
-
-  # Create delegate.
-  unless @delegate?
   @commandsMap = {}
   @groupsMap = {}
   @items = []
@@ -56,6 +45,16 @@ Menu::insert = (pos, item) ->
           break
         v8Util.setHiddenValue group[0], 'checked', true unless checked
 
+Menu::popup = (window) ->
+  throw new TypeError('Invalid window') unless window?.constructor is BrowserWindow
+  @_popup window
+
+Menu::append = (item) ->
+  @insert @getItemCount(), item
+
+Menu::insert = (pos, item) ->
+  throw new TypeError('Invalid item') unless item?.constructor is MenuItem
+
   switch item.type
     when 'normal' then @insertItem pos, item.commandId, item.label
     when 'checkbox' then @insertCheckItem pos, item.commandId, item.label