NamedBeanHolder enforces bean name

Issue: SPR-7549

spring-beans/src/main/java/org/springframework/beans/factory/config/NamedBeanHolder.java

@@ -17,6 +17,7 @@
 package org.springframework.beans.factory.config;
 
 import org.springframework.beans.factory.NamedBean;
+import org.springframework.util.Assert;
 
 /**
  * A simple holder for a given bean name plus bean instance.
@@ -34,20 +35,26 @@ public class NamedBeanHolder<T> implements NamedBean {
 
 	/**
 	 * Create a new holder for the given bean name plus instance.
+	 * @param beanName the name of the bean
+	 * @param beanInstance the corresponding bean instance
 	 */
 	public NamedBeanHolder(String beanName, T beanInstance) {
+		Assert.notNull(beanName, "Bean name must not be null");
 		this.beanName = beanName;
 		this.beanInstance = beanInstance;
 	}
 
 
+	/**
+	 * Return the name of the bean (never {@code null}).
+	 */
 	@Override
 	public String getBeanName() {
 		return this.beanName;
 	}
 
 	/**
-	 * Return the corresponding bean instance.
+	 * Return the corresponding bean instance (can be {@code null}).
 	 */
 	public T getBeanInstance() {
 		return this.beanInstance;