ENYO-591: Add invalid-page-index warning to 2.5 for QA purposes

At SoonGil Choi's request, adding warning to 2.5 to make it easier
for potential page-index issues to be discovered and reported by
QA, customer service, etc.

We think we have cleaned up the page-index assignment code to the
point where such errors will no longer occur, but since we have
recently suffered from a number of issues in this area and 2.5
will soon be released into production, we'll include this warning
to hedge our bets.

Enyo-DCO-1.1-Signed-Off-By: Gray Norton (gray.norton@lge.com)