Fix possible crash when fetching Nearby results.

Looks like the server sometimes replies with no "query" object, but no
"error" object either, which messes up our parsing of it. This way, we'll
abort processing the reply, and show the user a "could not retrieve
results" message, giving them a chance to refresh the results.

Bug: 72761
Change-Id: Ia0b33b94adaefdf4b32d360cd5a331d13ba7473b