Add null checks to MissedCallNotifier.

Bug: 16782303
Change-Id: I1ffee114315c20db33512082f9c0d25db8010988
diff --git a/res/values/strings.xml b/res/values/strings.xml
index ad8829c..f2f80ee 100644
--- a/res/values/strings.xml
+++ b/res/values/strings.xml
@@ -108,4 +108,7 @@
     <string name="test_account_2_short_description">Talk to everyone in your Circles!</string>
     <!-- DO NOT TRANSLATE. Short description for test Subscription 3. -->
     <string name="test_account_3_short_description">Chat with Chat Network users</string>
+
+    <!-- DO NOT TRANSLATE. Hardcoded number used for restricted incoming phone numbers. -->
+    <string name="handle_restricted">RESTRICTED</string>
 </resources>