BluetoothPairingRequest: Add null check for action

Bug: 159728132
Test: Build

Change-Id: I24668e20accf96c7469c9e1ab589b1383ab59d18
diff --git a/src/com/android/settings/bluetooth/BluetoothPairingRequest.java b/src/com/android/settings/bluetooth/BluetoothPairingRequest.java
index 7da6342..3cd21f5 100644
--- a/src/com/android/settings/bluetooth/BluetoothPairingRequest.java
+++ b/src/com/android/settings/bluetooth/BluetoothPairingRequest.java
@@ -34,7 +34,7 @@
   @Override
   public void onReceive(Context context, Intent intent) {
     String action = intent.getAction();
-    if (!action.equals(BluetoothDevice.ACTION_PAIRING_REQUEST)) {
+    if (action == null || !action.equals(BluetoothDevice.ACTION_PAIRING_REQUEST)) {
       return;
     }
     // convert broadcast intent into activity intent (same action string)