Duplicate row not working

[creo-code]

The documentation mentions a duplicate button:
https://github.com/contao-community-alliance/contao-multicolumnwizard-bundle#hide-buttons

$GLOBALS['TL_DCA']['tl_theme']['fields']['templateSelection'] = [
    ....
    'eval'      => [
        'buttons'      =>
        [
            'new'    => false,
            'copy'   => false,
            'delete' => false,
            'up'     => false,
            'down'   => false
        ],
        ...
    ],
    ...
];

When I try to set "copy" to true, the html code will be added but without a icon as image.

<a data-operations="copy" href="contao?act=edit&..." title="" onclick="return false;"></a>

After clicking the copy button nothing happens.
By digging further through the code I found out the script for the event was uncommented:
https://github.com/contao-community-alliance/contao-multicolumnwizard-bundle/blob/master/src/Resources/public/js/multicolumnwizard_be_src.js#L886-L887

If I remove the comment, the copy function works, except for a warning about the missing alt attribute from the missing .

Is there a reason this function was uncommented?