Unable to remove border option from table dialog

I am currently using the following code to remove elements from the table editing dialog - they all work apart from the 'txtBorder' one - can anybody exaplin why?

CKEDITOR.on('dialogDefinition', function(ev) {
    var dialogName = ev.data.name;
    var dialogDefinition = ev.data.definition;

    if (dialogName == 'table' || dialogName == 'tableProperties') {
        var contents = dialogDefinition.getContents('info');

        contents.remove('txtCellSpace');
        contents.remove('txtCellPad');
        contents.remove('txtCaption');
        contents.remove('txtSummary');

        contents.remove('txtBorder'); // Does not work
    }
});

I get the following error

x is null
    m=n.replace(/%2/g,l).replace(/%1/g,'ck...){o.setValue(q);l.fire('dataReady'); 

ckeditor.js (line 69)

I've had a look @ the table.js file and the border definition looks like everything else, has an idea so not sure why its not working.

Many thanks for any help on this!