Update lookup table managing code

Update lookup table managing code

 After 53607e033002977d350d84fb210b3f7fb372e776, there is a problem with
 lookup table manaing. Even when the lookup table is showing, focus out
 event cause committing preedit text. But in that case, the preedit string
 should not be committed. And the focus is in again, the last lookup table
 should be shown. So I've change the code to conform to this behavior.