fixing search in page chooser, which would allow selection of any page despite restrictions

When the developer adds a restriction on the `PageChooserPanel` to allow only insertion of a certain type of page, the editor was able to circumvent this by searching for the disallowed page. Choosing the page by navigating through the explorer was correctly prevented, but choosing from the search results didn't restrict the user at all.
This will only count the number of results on the first page.
I would recommend: ``pages.paginator.count``