findMethodAnnotation marked with @nullable

Author: rwinch

spring-graphql/src/main/java/org/springframework/graphql/data/method/annotation/support/AuthenticationPrincipalArgumentResolver.java

@@ -131,6 +131,7 @@ private boolean isInvalidType(MethodParameter parameter, @Nullable Object princi
 	 * @param parameter the {@link MethodParameter} to search for an {@link Annotation}
 	 * @return the {@link Annotation} that was found or null.
 	 */
+	@Nullable
 	private <T extends Annotation> T findMethodAnnotation(Class<T> annotationClass, MethodParameter parameter) {
 		T annotation = parameter.getParameterAnnotation(annotationClass);
 		if (annotation != null) {