Defensive check for null returned from createConnection()

Closes gh-29706

spring-jms/src/main/java/org/springframework/jms/support/JmsAccessor.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2022 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.
@@ -193,7 +193,13 @@ protected JmsException convertJmsAccessException(JMSException ex) {
 	 * @see javax.jms.ConnectionFactory#createConnection()
 	 */
 	protected Connection createConnection() throws JMSException {
-		return obtainConnectionFactory().createConnection();
+		ConnectionFactory cf = obtainConnectionFactory();
+		Connection con = cf.createConnection();
+		if (con == null) {
+			throw new javax.jms.IllegalStateException(
+					"ConnectionFactory returned null from createConnection(): " + cf);
+		}
+		return con;
 	}
 
 	/**