* parse.y (arg_blk_pass): preceeding arguments node may be NULL when
  an empty keyword argument hash splat is optimized away.
  [ruby-core:88890] [Bug #15087]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@64786 b2dd03c8-39d4-4d8f-98ff-823fe69b080e