When articles got inserted "pagebreaks" the content plugin "pagebreak" inserts at the bottom of the article a "ul" element with 2 navigation buttons "prev" and "next" just like this:

As you people can see, when the user is at the first or last page, the navigation elements shows a "li" element with just text which makes hard does some CSS styling to that element, to solve this problem I propose the just wrap the content of the first and last navigation element with a "span" element

the file to modify in question is https://github.com/joomla/joomla-cms/blob/master/plugins/content/pagebreak/pagebreak.php#L313

line: 313 and 323

With something like:

$next = "" . JText::_('JNEXT') . "";

and

$prev = "" . JText::_('JPREV') . "";

This change is minimum and doubt it will cause any kind of issue, and developers would be able to do some styles like this

.pagination li span { //style for disable button }
.pagination li a { //style for enabled button }

here is the pull request

#337

I hope I'm doing this correctly