Hacks to make demo search app work with GAE SDK 1.7.7

Essentially, we need to catch the exceptions that are thrown when zero
results are returned. See
https://code.google.com/p/googleappengine/issues/detail?id=9228 for the
driver for these changes.

There's undoubtedly a much better way to handle this at the SDK level.

Signed-off-by: Dan Scott <dan@coffeecode.net>