Add 2500 as default delay

src/components/views/settings/tabs/user/SecurityUserSettingsTab.js

@@ -129,7 +129,7 @@ export default class SecurityUserSettingsTab extends React.Component {
                 if (e.errcode === "M_LIMIT_EXCEEDED") {
                     // Add a delay between each invite change in order to avoid rate
                     // limiting by the server.
-                    await Promise.delay(e.retry_after_ms);
+                    await Promise.delay(e.retry_after_ms || 2500);
 
                     // Redo last action
                     i--;