Items per page bug?

OJS version 3.1.2.0
In dashboard, on page users & roles, there is a select box for selecting how menu users to show per page. I have noticed there is a NaN value, and I don’t think it should be there.

nan

I found function $.pkp.classes.features.PagingFeature.prototype.configItemsPerPageElement_
in file lib/pkp/js/classes/features/PagingFeature.js
on line 200, and changed:

itemsPerPageValues.push(options.defaultItemsPerPage);

to

if (!isNaN(options.defaultItemsPerPage)) {
itemsPerPageValues.push(options.defaultItemsPerPage);
}

Now select box works as it should, but I wonder if there is a better solution, and why is defaultItemsPerPage == NaN, and where this variable should be set?