Fix bug #16957601 Stability: ISE in Settings: Observer com.android.settings.
SettingsPreferenceFragment$1@273c8fdb was not registered

- add onUnbindPreferences() call to match onBindPreferences()
- this new method is @hide so it does not impact the APIs

Change-Id: Iee0ab8a4ecc2046f89fb96cc52af150e835f658c
1 file changed