Gallery Formatter Adjusting the Width of Gallery-Thumbs
make shure the empty li's have no width specified (or are now shown at all). change

&lt;li class="empty" style="width: 121px;"/&gt;


to

 &lt;li class="empty"/&gt;


if you cannot manage that - do it via css

.gallery-thumbs li.empty { width: 0px !important; }