Bug 33896: Check whether index is defined before string match

Bug 33896: Check whether index is defined before string match

This patch checks that $indexes[$i] is defined before testing whether the string matches to remove the logged warning when searching

Test plan:
1) In the intranet, search the catalog from the top search bar
2) Check plack-intranet-error.log
3) There should be a warning "[WARN] Use of uninitialized value within @indexes in string eq"
4) Apply patch
5) restart_all and then re-try the search
6) The warning should no longer appear

Signed-off-by: David Cook <dcook@prosentient.com.au>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>