Malformed Bearer Token Returns 401 for WebFlux

Fixes gh-7668

config/src/test/java/org/springframework/security/config/web/server/OAuth2ResourceServerSpecTests.java

@@ -172,6 +172,17 @@ public class OAuth2ResourceServerSpecTests {
 				.expectHeader().value(HttpHeaders.WWW_AUTHENTICATE, startsWith("Bearer error=\"invalid_token\""));
 	}
 
+	@Test
+	public void getWhenEmptyBearerTokenThenReturnsInvalidToken() {
+		this.spring.register(PublicKeyConfig.class).autowire();
+
+		this.client.get()
+				.headers(headers -> headers.add("Authorization", "Bearer "))
+				.exchange()
+				.expectStatus().isUnauthorized()
+				.expectHeader().value(HttpHeaders.WWW_AUTHENTICATE, startsWith("Bearer error=\"invalid_token\""));
+	}
+
 	@Test
 	public void getWhenValidTokenAndPublicKeyInLambdaThenReturnsOk() {
 		this.spring.register(PublicKeyInLambdaConfig.class, RootController.class).autowire();