BUG 45026: Fixed crasher (eltIndex wasn't being set on tok array)

* eltIndex wasn't being set on the token array being pushed onto
  the workstack in one case (code rewrite from commit 555ec42).

* The fix is trivial, but to prevent future bugs like this,
  I introduced a pushChunk function to use with the workStack
  which implicitly sets eltIndex onto the pushed array.

Change-Id: I06824004e80fe7619059361395f2f99ac30c410d