Menu Button may be missing default mode

[Jakub Ś]

1. Please insert attached file into plugins folder
2. On sample page please specify

   extraPlugins:'tracking',
   toolbar_Basic : [['Accept' ]]
   

3. Open sample, open menu button and click any option.

Problem: button gets disabled.

This is happening because plugin doesn't use modes: { wysiwyg: 1 }, (If you set it there is no problem). When I was looking through code of button.js plugin I haven't found any lines that sets modes, only lines that use mode property.
This is quite different from command.js which for example set default mode.

I believe that either there should be default mode for menu button or this property should be made required.

Problem can be reproduced in both CKEditor 4.x and 3.x