Check availability on start for TetherSettings

mUnavailable variable is only assigned when creating the activity. This make the app crash when we disable tethering and then resume + toggle on the Bluetooth Tethering. This cl remove the variable and directly check whenever the app start.

Bug: 270285631
Test: manual
Change-Id: I0dff1d11cbcc06816a69985f96eee828bb83e87c
1 file changed