Fix Null pointer exception on closing and update assets

...res/drawable-hdpi/btn_keyboard_key_normal_off_stone.9.png

.../res/drawable-hdpi/btn_keyboard_key_normal_on_stone.9.png

java/res/drawable-hdpi/btn_keyboard_key_normal_stone.9.png

...res/drawable-mdpi/btn_keyboard_key_normal_off_stone.9.png

.../res/drawable-mdpi/btn_keyboard_key_normal_on_stone.9.png

java/res/drawable-mdpi/btn_keyboard_key_normal_stone.9.png

java/src/com/android/inputmethod/latin/LatinIME.java

java/src/com/android/inputmethod/latin/LatinImeLogger.java