Ignore Content-Type that is invalid (not concrete)

Closes gh-27957

spring-web/src/test/java/org/springframework/http/server/ServletServerHttpRequestTests.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.
@@ -151,6 +151,13 @@ public class ServletServerHttpRequestTests {
 		assertThat(headers.getContentType()).isNull();
 	}
 
+	@Test // gh-27957
+	void getHeadersWithWildcardContentType() {
+		mockRequest.setContentType("*/*");
+		mockRequest.removeHeader("Content-Type");
+		assertThat(request.getHeaders()).as("Invalid content-type should not raise exception").hasSize(0);
+	}
+
 	@Test
 	void getBody() throws IOException {
 		byte[] content = "Hello World".getBytes(StandardCharsets.UTF_8);