test: add a missing test

It is for 788312a0a8d6dd013933c84524c937fb0ed69bd6:

    Fix a crash bug

    It causes by offline index construction for vector column that has
    orphan reference. Groonga should avoid the case (e.g. groonga returns
    an error for removing table that is referred from any column) but
    this fix will be useful a bit to make groonga more robust.