Fix connectionRegistry check

bramble-core/src/main/java/org/briarproject/bramble/mailbox/MailboxServiceImpl.java

@@ -189,7 +189,7 @@ public class MailboxServiceImpl implements MailboxService, EventListener {
 		@Override
 		public void run() {
 			if (hasPrivateMailbox.get() &&
-					connectionRegistry.isConnected(privateMailboxId)) {
+					!connectionRegistry.isConnected(privateMailboxId)) {
 				try {
 					connectPrivateMailbox();
 				} catch (DbException e) {