Fixed a bug in grn_obj_set_value() that empty value was not updated correctly.
Fixed a bug in grn_obj_set_value() that empty value was not updated correctly.

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