Make ImprovDevice name nullable [breaking change]

[jpelgrom]

Make the name of ImprovDevices nullable to fix the following crash that may occur:

FATAL EXCEPTION: main
java.lang.NullPointerException: name must not be null
	at com.wifi.improv.ImprovManager$scanCallback$1.onScanResult(ImprovManager.kt:46)
	at android.bluetooth.le.BluetoothLeScanner$BleScanCallbackWrapper$1.run(BluetoothLeScanner.java:568)
	at android.os.Handler.handleCallback(Handler.java:959)
	at android.os.Handler.dispatchMessage(Handler.java:100)
	at android.os.Looper.loopOnce(Looper.java:232)
	at android.os.Looper.loop(Looper.java:317)
	at android.app.ActivityThread.main(ActivityThread.java:8592)
	at java.lang.reflect.Method.invoke(Native Method)
	at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:580)
	at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:878)

The library already acknowledge that it may be null internally:

sdk-android/library/src/main/java/com/wifi/improv/ImprovManager.kt

Line 44 in 9def544

Log.i(TAG, "Found BLE device! Name: ${name ?: "Unnamed"}, address: $address")