avoid failures in case of manually registered null instance (SPR-7523)

org.springframework.context/src/test/java/org/springframework/context/support/GenericApplicationContextTests.java

@@ -0,0 +1,36 @@
+/*
+ * Copyright 2002-2010 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.context.support;
+
+import org.junit.Test;
+
+import org.springframework.beans.factory.support.DefaultListableBeanFactory;
+
+/**
+ * @author Juergen Hoeller
+ * @author Chris Beams
+ */
+public class GenericApplicationContextTests {
+
+	@Test
+	public void nullBeanRegistration() {
+			DefaultListableBeanFactory bf = new DefaultListableBeanFactory();
+			bf.registerSingleton("nullBean", null);
+			new GenericApplicationContext(bf).refresh();
+	}
+
+}