add a test for selecting by nonexistent reference key.
add a test for selecting by nonexistent reference key.

Now, this test is failed.

hiroyuki-sato/groonga,redfigure/groonga,hiroyuki-sato/groonga,redfigure/groonga,kenhys/groonga,komainu8/groonga,kenhys/groonga,myokoym/groonga,cosmo0920/groonga,redfigure/groonga,naoa/groonga,myokoym/groonga,cosmo0920/groonga,myokoym/groonga,cosmo0920/groonga,redfigure/groonga,myokoym/groonga,kenhys/groonga,naoa/groonga,komainu8/groonga,komainu8/groonga,naoa/groonga,groonga/groonga,groonga/groonga,myokoym/groonga,hiroyuki-sato/groonga,hiroyuki-sato/groonga,kenhys/groonga,kenhys/groonga,naoa/groonga,cosmo0920/groonga,groonga/groonga,hiroyuki-sato/groonga,komainu8/groonga,groonga/groonga,redfigure/groonga,myokoym/groonga,hiroyuki-sato/groonga,naoa/groonga,kenhys/groonga,naoa/groonga,komainu8/groonga,komainu8/groonga,cosmo0920/groonga,komainu8/groonga,cosmo0920/groonga,naoa/groonga,naoa/groonga,myokoym/groonga,komainu8/groonga,redfigure/groonga,cosmo0920/groonga,redfigure/groonga,kenhys/groonga,cosmo0920/groonga,hiroyuki-sato/groonga,kenhys/groonga,groonga/groonga,groonga/groonga,myokoym/groonga,groonga/groonga,groonga/groonga,hiroyuki-sato/groonga,redfigure/groonga