add contactId check in ContactMailboxSession

bramble-core/src/main/java/org/briarproject/bramble/mailbox/sessions/ContactMailboxSession.java

@@ -109,6 +109,11 @@ public class ContactMailboxSession extends AbstractMailboxSession {
 		public void handleRequest(MailboxRequest request)
 				throws ProtocolException {
 			MailboxRequestTake takeRequest = (MailboxRequestTake) request;
+
+			if (takeRequest.hasContactId())
+				throw new ProtocolException(
+						"TAKE request from contact mailbox must not have contactId");
+
 			InputStream in = new ByteArrayInputStream(
 					takeRequest.getEncryptedSyncStream());
 			try {