Make sure campaign data isn't set to false

If for some reason the stored data can't be properly unserialized
(e.g. there's a syntax error), unserialize() will return false. We
should catch this condition rather than passing false as the value
to the client.

Change-Id: I635243f00917d6c6c683d2aab29e71296608e996
Merge "Make sure campaign data isn't set to false"