修复SimpleServer在添加的HttpFilter中有获取请求参数时报错问题

hutool-http/src/test/java/cn/hutool/http/server/Issue3343Test.java

@@ -0,0 +1,33 @@
+package cn.hutool.http.server;
+
+import cn.hutool.core.date.DateUtil;
+import cn.hutool.core.lang.Console;
+import cn.hutool.core.map.multi.ListValueMap;
+import cn.hutool.http.HttpUtil;
+
+/**
+ * http://localhost:8888/?name=hutool
+ */
+public class Issue3343Test {
+	public static void main(final String[] args) {
+		final SimpleServer server = HttpUtil.createServer(8888)
+			.addFilter((req, res, chain) -> {
+				Console.log(DateUtil.now() + " got request: " + req.getPath());
+				Console.log(" >   from : " + req.getClientIP());
+				// 过滤器中获取请求参数
+				Console.log(" > params : " + req.getParams());
+				chain.doFilter(req.getHttpExchange());
+			});
+
+		server.addAction("/", Issue3343Test::index);
+
+		server.start();
+	}
+
+	private static void index(HttpServerRequest request, HttpServerResponse response) {
+		// 具体逻辑中再次获取请求参数
+		ListValueMap<String, String> params = request.getParams();
+		Console.log("index params: " + params);
+		response.getWriter().write("GOT: " + params);
+	}
+}