Only set UNRESTRICTED mode if recipients have a non-null verifier.

Otherwise we could send UD messages to people with non-UD linked
devices.

src/org/thoughtcrime/securesms/jobs/RetrieveProfileJob.java

@@ -171,7 +171,7 @@ public class RetrieveProfileJob extends ContextJob implements InjectableType {
     RecipientDatabase recipientDatabase = DatabaseFactory.getRecipientDatabase(context);
     byte[]            profileKey        = recipient.getProfileKey();
 
-    if (unrestrictedUnidentifiedAccess) {
+    if (unrestrictedUnidentifiedAccess && unidentifiedAccessVerifier != null) {
       Log.i(TAG, "Marking recipient UD status as unrestricted.");
       recipientDatabase.setUnidentifiedAccessMode(recipient, UnidentifiedAccessMode.UNRESTRICTED);
     } else if (profileKey == null || unidentifiedAccessVerifier == null) {