Fix navigation buttons on Special:Listfiles for first and last page

The listfiles pager was appending the username to the paging queries
for all paging queries. On the first/last page, this was appending
the username to false, thus marking the first/last page as still having
further results despite that not being the case.

Bug: 67627
Change-Id: Ib302a826fa638d7ae25c6d37951277fa8701ab69
Merge "Fix navigation buttons on Special:Listfiles for first and last page"