don't send empty params on subscribe, config clarifications

server/tinode.conf

@@ -136,12 +136,13 @@
 			"serial_num": 1,
 
 			// Secret key (HMAC salt) for signing the tokens. Generate your own then keep it secret.
-			// 32 random bytes base64 encioded.
+			// Any 32 random bytes base64 encoded.
 			//
 			// === IMPORTANT ===
 			//
 			// CHANGE IT IN PRODUCTION!!! Otherwise anyone will be able to log in
-			// to your server without the password.
+			// to your server without the password. It's just random bytes, use any suitable
+			// means to get it.
 			"key": "wfaY2RgF2S1OQI/ZlK+LSrp1KB2jwAdGAIHQ7JZn+Kc="
 		}
 	},
@@ -282,15 +283,15 @@
 				// Then insert the file contents here. Yes, this is convoluted, but that's Google's fault.
 				"credentials": {
 					"type": "service_account",
-  					"project_id": "your-project-id",
-  					"private_key_id": "some-random-looking-hex-number",
-  					"private_key": "-----BEGIN PRIVATE KEY----- base64-encoded bits of your private key \n-----END PRIVATE KEY-----\n",
-  					"client_email": "firebase-adminsdk-abc123@your-project-id.iam.gserviceaccount.com",
-  					"client_id": "1234567890123456789",
-  					"auth_uri": "https://accounts.google.com/o/oauth2/auth",
-  					"token_uri": "https://oauth2.googleapis.com/token",
-  					"auth_provider_x509_cert_url": "https://www.googleapis.com/oauth2/v1/certs",
-  					"client_x509_cert_url": "https://www.googleapis.com/robot/v1/metadata/x509/firebase-adminsdk-abc123%40your-project-id.iam.gserviceaccount.com"
+						"project_id": "your-project-id",
+						"private_key_id": "some-random-looking-hex-number",
+						"private_key": "-----BEGIN PRIVATE KEY----- base64-encoded bits of your private key \n-----END PRIVATE KEY-----\n",
+						"client_email": "firebase-adminsdk-abc123@your-project-id.iam.gserviceaccount.com",
+						"client_id": "1234567890123456789",
+						"auth_uri": "https://accounts.google.com/o/oauth2/auth",
+						"token_uri": "https://oauth2.googleapis.com/token",
+						"auth_provider_x509_cert_url": "https://www.googleapis.com/oauth2/v1/certs",
+						"client_x509_cert_url": "https://www.googleapis.com/robot/v1/metadata/x509/firebase-adminsdk-abc123%40your-project-id.iam.gserviceaccount.com"
 				},
 
 				// An alternative way to provide Firebase service account credentials.

server/topic.go

@@ -861,6 +861,12 @@ func (t *Topic) subCommonReply(h *Hub, sreg *sessionJoin) error {
 	if sreg.created && sreg.pkt.topic != toriginal {
 		params["tmpname"] = sreg.pkt.topic
 	}
+
+	if len(params) == 0 {
+		// Don't send empty params '{}'
+		params = nil
+	}
+
 	sreg.sess.queueOut(NoErrParams(sreg.pkt.id, toriginal, now, params))
 
 	return nil