Fix exception in Jetty10RequestUpgradeStrategy

Closes gh-27899

Author: rstoyanchev

spring-webflux/src/main/java/org/springframework/web/reactive/socket/server/upgrade/Jetty10RequestUpgradeStrategy.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2021 the original author or authors.
+ * Copyright 2002-2022 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -149,7 +149,7 @@ public WebSocketCreatorInterceptor(
 		public Object invoke(@NonNull MethodInvocation invocation) {
 			if (this.protocol != null) {
 				ReflectionUtils.invokeMethod(
-						setAcceptedSubProtocol, invocation.getArguments()[2], this.protocol);
+						setAcceptedSubProtocol, invocation.getArguments()[1], this.protocol);
 			}
 			return this.adapter;
 		}

spring-websocket/src/main/java/org/springframework/web/socket/server/jetty/Jetty10RequestUpgradeStrategy.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2021 the original author or authors.
+ * Copyright 2002-2022 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -158,7 +158,7 @@ public WebSocketCreatorInterceptor(
 		public Object invoke(@NonNull MethodInvocation invocation) {
 			if (this.protocol != null) {
 				ReflectionUtils.invokeMethod(
-						setAcceptedSubProtocol, invocation.getArguments()[2], this.protocol);
+						setAcceptedSubProtocol, invocation.getArguments()[1], this.protocol);
 			}
 			return this.adapter;
 		}