Avoid NPEs when BluetoothDevice.getName() returns null

app/src/main/java/nodomain/freeyourgadget/gadgetbridge/impl/GBDevice.java

@@ -59,7 +59,7 @@ public class GBDevice implements Parcelable {
 
     public GBDevice(String address, String name, DeviceType deviceType) {
         mAddress = address;
-        mName = name;
+        mName = (name != null) ? name : mAddress;
         mDeviceType = deviceType;
         validate();
     }