fix(XMPP): Get the correct domain for XMPP ping.

modules/xmpp/XmppConnection.js

@@ -175,6 +175,13 @@ export default class XmppConnection extends Listenable {
         return this._stropheConn.options;
     }
 
+    /**
+     * A getter for the domain to be used for ping.
+     */
+    get pingDomain() {
+        return this._options.pingOptions?.domain || this.domain;
+    }
+
     /**
      * A getter for the service URL.
      *

modules/xmpp/xmpp.js

@@ -540,8 +540,7 @@ export default class XMPP extends Listenable {
      */
     ping(timeout) {
         return new Promise((resolve, reject) => {
-            this.connection.ping
-                    .ping(this.connection.options.hosts.domain, resolve, reject, timeout);
+            this.connection.ping.ping(this.connection.pingDomain, resolve, reject, timeout);
         });
     }