fix: implement 'login' event for net.ClientRequest (#21096)

lib/browser/api/net.js

@@ -247,22 +247,11 @@ class ClientRequest extends EventEmitter {
     })
 
     urlRequest.on('login', (event, authInfo, callback) => {
-      this.emit('login', authInfo, (username, password) => {
-        // If null or undefined username/password, force to empty string.
-        if (username === null || username === undefined) {
-          username = ''
-        }
-        if (typeof username !== 'string') {
-          throw new Error('username must be a string')
-        }
-        if (password === null || password === undefined) {
-          password = ''
-        }
-        if (typeof password !== 'string') {
-          throw new Error('password must be a string')
-        }
-        callback(username, password)
-      })
+      const handled = this.emit('login', authInfo, callback)
+      if (!handled) {
+        // If there were no listeners, cancel the authentication request.
+        callback()
+      }
     })
 
     if (callback) {