Bug 17790: Fix js error on undefined autocomplete(...).data(...)

Bug 17790: Fix js error on undefined autocomplete(...).data(...)

Bug 17418 moved some code to js_includes.inc.
But if #findborrower does not exist, you cannot define _renderItem.
Trivial fix.

Test plan:
[1] Find a page where this include is used and #findborrowers is absent.
    Like about.pl
[2] Without this patch, you will have a js error in the js console.
[3] With this patch, you should no longer have it.

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Jonathan Druart <jonathan.druart@biblibre.com>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>