If near the end of the pagination for search results and the end user changes their results to a large page size an error can occur.

Most likely what is occurring is that the page number never changes, but the number of pages is actually less then what is selected in the url because of the results per page size.

For example...

A User has 20 results per page, has 100 total results from their search query, and is on page 5 of their results (the last page).

If that User changes their results per page size to 50, there will only be 2 pages of results, but the User is directed to page 5 (the page they were last on). Since there are really only 2 pages now, a exception occurs.