Fix BindingReflectionHintsRegistrar anonymous classes support

This commit ensures that giving an anonymous class for reflection hints
registration does not result in a NullPointerException, since the
canonical name of anonymous classes is null.

Fixes gh-29657

spring-core/src/test/java/org/springframework/aot/hint/BindingReflectionHintsRegistrarTests.java

@@ -221,6 +221,12 @@ public class BindingReflectionHintsRegistrarTests {
 				});
 	}
 
+	@Test
+	void registerTypeForSerializationWithAnonymousClass() {
+		Runnable anonymousRunnable = () -> { };
+		bindingRegistrar.registerReflectionHints(this.hints.reflection(), anonymousRunnable.getClass());
+	}
+
 	@Test
 	void registerTypeForJacksonAnnotations() {
 		bindingRegistrar.registerReflectionHints(this.hints.reflection(), SampleClassWithJsonProperty.class);