Stopgap solution for a crash.

This returns the wrong string, but since it's used for getting the
previous word for bigrams, it only results in slightly worse
suggestions quality.
Cherry-pick of I6ce5de2f

Bug: 11273655
Change-Id: I17fb6d74f18fb31bd8f8518f80456d74ae30a2c3
1 file changed
tree: d28cddd30daff74198feca246f8ab81dabacea28
  3. dictionaries/
  4. java/
  5. native/
  6. tests/
  7. tools/