Guard for null pointer if no host header.

Fixes gh-3699

Author: spencergibb

spring-cloud-gateway-server-mvc/src/main/java/org/springframework/cloud/gateway/server/mvc/predicate/GatewayRequestPredicates.java

@@ -374,6 +374,9 @@ private static class HostPatternPredicate implements RequestPredicate, ChangePat
 		@Override
 		public boolean test(ServerRequest request) {
 			String host = request.headers().firstHeader(HttpHeaders.HOST);
+			if (host == null) {
+				host = "";
+			}
 			PathContainer pathContainer = PathContainer.parsePath(host, PathContainer.Options.MESSAGE_ROUTE);
 			PathPattern.PathMatchInfo info = this.pattern.matchAndExtract(pathContainer);
 			traceMatch("Pattern", this.pattern.getPatternString(), host, info != null);

spring-cloud-gateway-server-mvc/src/test/java/org/springframework/cloud/gateway/server/mvc/predicate/GatewayRequestPredicatesTests.java

@@ -0,0 +1,37 @@
+/*
+ * Copyright 2013-2025 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.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.cloud.gateway.server.mvc.predicate;
+
+import java.util.Collections;
+
+import org.assertj.core.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+import org.springframework.mock.web.MockHttpServletRequest;
+import org.springframework.web.servlet.function.ServerRequest;
+
+public class GatewayRequestPredicatesTests {
+
+	@Test
+	void nullHostPassedToHostPredicate() {
+		MockHttpServletRequest servletRequest = new MockHttpServletRequest();
+		ServerRequest serverRequest = ServerRequest.create(servletRequest, Collections.emptyList());
+		boolean result = GatewayRequestPredicates.host("*.myhost.org").test(serverRequest);
+		Assertions.assertThat(result).isFalse();
+	}
+
+}