Move some treatment to a more sensical place.

It makes more sense to catch words with the safety net in
updateSuggestions() than in showSuggestions(). Also, it's useless
to do it in updateBigramPredictions, because the result will
always be provably false.
This will also help with writing unit tests.

Change-Id: Ifab81e6c5a74b1aa75cf85ef7742fee69a98f5ce