Do not commit pending text upon key event received from input method.

A common usecase for this is when preedit is not empty, but key event is bypassed is when modifier key is pressed. For example, user may want to send Shift+A to input method, but input method will ignore the Shift key press and forward shift to application. This allows certain usecase if application reacts to modifier only key event.

While it "may" causes some issue when input method decide to send key that produce text when preedit is not empty, this does not happen in practice and should be considered a bug on input method engine side.