NfcProvisioning: Fix NPE on devices without NFC

This sample is basically useless on devices without NFC, but we need
this just to make tests pass on the emulator running on our CI server.

Bug: 19918931

Change-Id: I80db8e5fbf84c78039ecde52f2b4131bf0bb52d7
diff --git a/admin/NfcProvisioning/Application/src/main/java/com/example/android/nfcprovisioning/NfcProvisioningFragment.java b/admin/NfcProvisioning/Application/src/main/java/com/example/android/nfcprovisioning/NfcProvisioningFragment.java
index e3b14c6..f46d0f2 100644
--- a/admin/NfcProvisioning/Application/src/main/java/com/example/android/nfcprovisioning/NfcProvisioningFragment.java
+++ b/admin/NfcProvisioning/Application/src/main/java/com/example/android/nfcprovisioning/NfcProvisioningFragment.java
@@ -94,7 +94,9 @@
         super.onStart();
         Activity activity = getActivity();
         NfcAdapter adapter = NfcAdapter.getDefaultAdapter(activity);
-        adapter.setNdefPushMessageCallback(this, activity);
+        if (adapter != null) {
+            adapter.setNdefPushMessageCallback(this, activity);
+        }
         getLoaderManager().initLoader(LOADER_PROVISIONING_VALUES, null, this);
     }