don't disable lockscreen widgets on low memory devices (2/2)

Change-Id: Iec97a60097075fde973b6928e1f21f3827e0325b
Fix one NPE in tethering setting

Once we not declare BT feature, go Setting->more->tethering
will trigger this NPE.
Cherry-picked from AOSP: https://android-review.googlesource.com/#/c/63695/

Change-Id: I4736e7bade261475acda74e26250a81452018ffa
Signed-off-by: Jianzheng Zhou <jianzheng.zhou@freescale.com>