Custom save button

I want to add a custom "save" button to my Editor; here is my code:

CKEDITOR.plugins.add('mysave',
{
    init: function (editor) {

        editor.addCommand('mysave',
         {
             exec: function (editor) {
            // Save the content to database using Ajax
              // ....
                 editor.destroy(false);
             }
         });

        editor.ui.addButton('MySave',
      {
          label: 'Save',
          command: 'mysave',
          icon: this.path + 'images/disk.png'
      });
    }
});

The problem is the "editor.destroy" call. I call it to hide the Editor and display the html but I get an error:

M is null
http://localhost/MySite/ckeditor_3.6.2/ckeditor.js
Line 100

What is wrong? Should I use another method than destroy?