Remove stale entry from users map

src/examples/secure-chat-client.ts

@@ -49,6 +49,7 @@ function runSession(t: Turn, uid: UserId, session: Ref) {
         return (_t) => {
             if (users.get(ui.uid) === ui.name) {
                 console.log(`${ui.name} departed`);
+                users.delete(ui.uid);
             }
         };
     }));