Ensure concurrent WebSocketSession wrapper is used

Issue: SPR-13326

Author: rstoyanchev

spring-websocket/src/main/java/org/springframework/web/socket/messaging/SubProtocolWebSocketHandler.java

@@ -305,9 +305,12 @@ else if (this.protocolHandlers.size() == 1) {
 	 */
 	@Override
 	public void handleMessage(WebSocketSession session, WebSocketMessage<?> message) throws Exception {
+		WebSocketSessionHolder holder = this.sessions.get(session.getId());
+		if (holder != null) {
+			session = holder.getSession();
+		}
 		SubProtocolHandler protocolHandler = findProtocolHandler(session);
 		protocolHandler.handleMessageFromClient(session, message, this.clientInboundChannel);
-		WebSocketSessionHolder holder = this.sessions.get(session.getId());
 		if (holder != null) {
 			holder.setHasHandledMessages();
 		}