fix null pointer exception

Bug: 123329829
Change-Id: I544b9599dca628cf80f36f9f2a9474ea61d6f12c
diff --git a/src/com/android/phone/PhoneInterfaceManager.java b/src/com/android/phone/PhoneInterfaceManager.java
index 9b3a4db..d10d3b5 100755
--- a/src/com/android/phone/PhoneInterfaceManager.java
+++ b/src/com/android/phone/PhoneInterfaceManager.java
@@ -5123,6 +5123,7 @@
         final Phone phone = getPhone(subId);
         if (phone == null) {
             log("getSimLocaleForSubscriber, invalid subId");
+            return null;
         }
         final long identity = Binder.clearCallingIdentity();
         try {