Android: Added guards for null values when checking if Bluetooth is turned on.
Android: Added guards for null values when checking if Bluetooth is turned on.

divineprog/cordova-ble,divineprog/cordova-ble,mikaelkindborg/cordova-ble,divineprog/cordova-ble,mikaelkindborg/cordova-ble,evothings/cordova-ble,evothings/cordova-ble,mikaelkindborg/cordova-ble,evothings/cordova-ble