grn_inspect(): fix a memory leak
grn_inspect(): fix a memory leak

We shouldn't write value to shallow copy bulk. It isn't freed. We should
just set reference.

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