msg.ctrl could be null if connection is already established

Author: or-else

tinodesdk/src/main/java/co/tinode/tinodesdk/Topic.java

@@ -901,7 +901,7 @@ public PromisedReply<ServerMessage> subscribe(MsgSetMeta<DP, DR> set, MsgGetMeta
                 new PromisedReply.SuccessListener<ServerMessage>() {
                     @Override
                     public PromisedReply<ServerMessage> onSuccess(ServerMessage msg) {
-                        if (msg.ctrl.code >= 300) {
+                        if (msg.ctrl == null || msg.ctrl.code >= 300) {
                             // 3XX response: already subscribed.
                             mAttached = true;
                             return null;