Wikimedia Bugzilla is closed!

I found that if I set a wrong or an empty value in the icon field of a toolbar button in the file « jquery.wikiEditor.toolbar.config.js » it displays the label instead of the icon.

'tt': {
    'label': 'tt',
    'type': 'button',
    'icon': 'noicon.jpg',
    'action': {
        'type': 'encapsulate',
        'options': {
            'pre': "<tt>",
            'post': "</tt>"
        }
    }
},

It is very useful because the text is well render comparing to text inside png icons. Svg icons have better rendering but it is easier to use the label than to create svg icons.
But if I use wrong or an empty value in the icon field, I have the following error:

[error] open() "/srv/http/mywiki/extensions/WikiEditor/modules/images/toolbar/noicon.jpg" failed (2: No such file or directory)

So, I would like to know how to display the label in a toolbar button without having the previous error.