Hi Eric,
There is no such thing as a "cloze quiz" in Moodle; I expect you mean you were creating a question of the Cloze question type. It would be much easier for us to understand your problem if you posted here the exact contents of the particular question which triggered the Warning message.
Anyway, as you have found out, such Warning (or Notices) messages which are displayed in debug mode do not prevent your Moodle quiz from working, so there is no need to worry.
All the best,
Joseph