fix a bug in SearchCache::get()
fix a bug in SearchCache::get()

which only affects distributed search

pombredanne/sf1r-lite,pombredanne/sf1r-lite,izenecloud/sf1r-lite,pombredanne/sf1r-lite,pombredanne/sf1r-lite,izenecloud/sf1r-lite,izenecloud/sf1r-lite,izenecloud/sf1r-ad-delivery,izenecloud/sf1r-ad-delivery,izenecloud/sf1r-lite,izenecloud/sf1r-ad-delivery,izenecloud/sf1r-ad-delivery,izenecloud/sf1r-ad-delivery,pombredanne/sf1r-lite,izenecloud/sf1r-lite