CBQE-0: fix KeyError

Change-Id: I1f5e8e9a5c3f0820204fad6d9ea06078f83dbcf8
Reviewed-on: http://review.couchbase.org/32808
Reviewed-by: Iryna Mironava <irynamironava@yandex.ru>
Tested-by: Iryna Mironava <irynamironava@yandex.ru>