Bug 36986: (follow-up) Ensure idempotency

MySQL/MariaDB checks the primary key/unique constraint before WHERE
clause when performing an UPDATE. As such, the lack of AutoLocation
existing will not prevent a failure on a second run of the update.

Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>

installer/data/mysql/db_revs/240600001.pl

@@ -10,7 +10,7 @@ return {
 
         $dbh->do(
             q{
-            UPDATE systempreferences SET variable = "StaffLoginLibraryBasedOnIP"
+            UPDATE IGNORE systempreferences SET variable = "StaffLoginLibraryBasedOnIP"
             WHERE variable = "StaffLoginBranchBasedOnIP"
         }
             ) == 1