Fix null pointer exception for devices without Bluetooth.

Change-Id: If44089824fe48b302f6e75ccbbfb3a6843016723

android/sdremote/src/org/libreoffice/impressremote/communication/CommunicationService.java

@@ -302,6 +302,10 @@ public class CommunicationService extends Service implements Runnable, MessagesL
     }
 
     private void restoreBluetoothState() {
+        if (!BluetoothOperator.isStateValid(mBluetoothState)) {
+            return;
+        }
+
         if (mBluetoothState.wasBluetoothEnabled()) {
             return;
         }

android/sdremote/src/org/libreoffice/impressremote/util/BluetoothOperator.java

@@ -39,9 +39,17 @@ public final class BluetoothOperator {
     }
 
     public static State getState() {
+        if (!isAvailable()) {
+            return null;
+        }
+
         return new State(getAdapter().isEnabled());
     }
 
+    public static boolean isStateValid(State aState) {
+        return aState != null;
+    }
+
     public static void enable() {
         if (!isAvailable()) {
             return;