CKEditor Destroy Shared Toolbar

So I have this code to create an editor with a shared toolbar:

var editor = $('#' + elementId).ckeditor({
   sharedSpaces:{
       top:'SharedToolbar'
   },
   toolbar:[
       ['Bold','Italic','Underline','Strike','-','Subscript','Superscript'],
       ['NumberedList','BulletedList','-','Outdent','Indent','Blockquote']
   ],

   removePlugins : 'maximize,resize,elementspath'
});

then I have this code to destroy it, from a button click:

var instance = CKEDITOR.instances[elementId];

if (instance) {
    instance.destroy();

    container.find('.control_edit').show();

    if ($.isEmptyObject(CKEDITOR.instances)){
        alert('Rar');
    }
}

However, once the destroy is executed, I get this error:

i.contentWindow is null

which may probably mean that a toolbar exists without its editor. SO I was wondering how I can destroy the shared toolbar along with the editor too?