Application crashes when Bluetooth is disabled

[assert-not-singularity]

When starting the application and Bluetooth is globally disabled in Android, the application crashes.

How to reproduce:

1. Turn of bluetooth
2. Start application with debugger attached

Expected behaviour:
Application requests user to turn on bluetooth or turns bluetooth on by itself.

Actual behaviour:
Application crashes with the following exception:

E/AndroidRuntime: FATAL EXCEPTION: main Process: app.bandemic, PID: 2171 java.lang.RuntimeException: Unable to create service app.bandemic.strict.service.TracingService: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.bluetooth.le.BluetoothLeAdvertiser.startAdvertising(android.bluetooth.le.AdvertiseSettings, android.bluetooth.le.AdvertiseData, android.bluetooth.le.AdvertiseCallback)' on a null object reference at android.app.ActivityThread.handleCreateService(ActivityThread.java:3581) at android.app.ActivityThread.access$1300(ActivityThread.java:201) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1672) at android.os.Handler.dispatchMessage(Handler.java:106) at android.os.Looper.loop(Looper.java:193) at android.app.ActivityThread.main(ActivityThread.java:6745) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858) Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.bluetooth.le.BluetoothLeAdvertiser.startAdvertising(android.bluetooth.le.AdvertiseSettings, android.bluetooth.le.AdvertiseData, android.bluetooth.le.AdvertiseCallback)' on a null object reference at app.bandemic.strict.service.BleAdvertiser.startAdvertising(BleAdvertiser.java:74) at app.bandemic.strict.service.TracingService.onCreate(TracingService.java:109) at android.app.ActivityThread.handleCreateService(ActivityThread.java:3569) at android.app.ActivityThread.access$1300(ActivityThread.java:201)  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1672)  at android.os.Handler.dispatchMessage(Handler.java:106)  at android.os.Looper.loop(Looper.java:193)  at android.app.ActivityThread.main(ActivityThread.java:6745)  at java.lang.reflect.Method.invoke(Native Method)  at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)