Avoid exposeTargetClass attempt if bean name is null

Issue: SPR-13650

Author: jhoeller

spring-aop/src/main/java/org/springframework/aop/framework/autoproxy/AutoProxyUtils.java

@@ -94,14 +94,14 @@ public static Class<?> determineTargetClass(ConfigurableListableBeanFactory bean
 	}
 
 	/**
-	 * Expose the given target class for the specified bean.
+	 * Expose the given target class for the specified bean, if possible.
 	 * @param beanFactory the containing ConfigurableListableBeanFactory
 	 * @param beanName the name of the bean
 	 * @param targetClass the corresponding target class
 	 * @since 4.2.3
 	 */
 	static void exposeTargetClass(ConfigurableListableBeanFactory beanFactory, String beanName, Class<?> targetClass) {
-		if (beanFactory.containsBeanDefinition(beanName)) {
+		if (beanName != null && beanFactory.containsBeanDefinition(beanName)) {
 			beanFactory.getMergedBeanDefinition(beanName).setAttribute(ORIGINAL_TARGET_CLASS_ATTRIBUTE, targetClass);
 		}
 	}