bluetooth: Don't crash when the local adapter is not set

In devices where bluetooth is not working (like the emulator or devices
in development), the bluetooth Settings crashes when closing the activity.

Most of the code checks for the nullability of the local adapter except
for this particular piece. This is usually not a worry for production
devices and I wouldn't usually worry about this but since the rest of the
code performs the nullability check it seems silly to crash onPause.

Change-Id: I7c1d3b43969b516336be770957008ef2054d312f
privacy: Actually set the blacklist preference

The preference was not being set, which caused this code to throw an NPE on
devices without telephony when opening the privacy preferences.

This bug also affects devices with telephony in that the preference doesn't
update its text. I also got rid of the null check because the preference
always exists, the null check is pointless and ended up hiding this bug.

Change-Id: I95555d44349700a8f29a71a2f2ee9aedf419b49b