Fix InputMethodPreference.compareTo method

Fixes: 64232283
Test: bit SettingsLibTests:com.android.settingslib.inputmethod.InputMethodPreferenceTest
      bit SettingsLibTests:com.android.settingslib.inputmethod.InputMethodSubtypePreferenceTest
Change-Id: I5b18e8c854dc6a8e4ff35aa356c9acd63acd3a53
4 files changed