(Bug 48528) Fix bug with null Zero config

* when renderZeroRatedBanner=true in URL, but the incoming request is not marked with X-CS parameter, avoids null-ref warning and blanking out of the page

Change-Id: I381b5c2a9e1e6373569aefeb2a6dc897cc9f16ce
Merge "(Bug 48528) Fix bug with null Zero config"