JavaMailSenderImpl calls sendMessage with empty array instead of null

Issue: SPR-17540

(cherry picked from commit 16e9b83d43)

spring-context-support/src/main/java/org/springframework/mail/javamail/JavaMailSenderImpl.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2015 the original author or authors.
+ * Copyright 2002-2018 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.
@@ -24,6 +24,7 @@ import java.util.List;
 import java.util.Map;
 import java.util.Properties;
 import javax.activation.FileTypeMap;
+import javax.mail.Address;
 import javax.mail.AuthenticationFailedException;
 import javax.mail.MessagingException;
 import javax.mail.NoSuchProviderException;
@@ -390,7 +391,7 @@ public class JavaMailSenderImpl implements JavaMailSender {
 
 	/**
 	 * Actually send the given array of MimeMessages via JavaMail.
-	 * @param mimeMessages MimeMessage objects to send
+	 * @param mimeMessages the MimeMessage objects to send
 	 * @param originalMessages corresponding original message objects
 	 * that the MimeMessages have been created from (with same array
 	 * length and indices as the "mimeMessages" array), if any
@@ -445,7 +446,8 @@ public class JavaMailSenderImpl implements JavaMailSender {
 						// Preserve explicitly specified message id...
 						mimeMessage.setHeader(HEADER_MESSAGE_ID, messageId);
 					}
-					transport.sendMessage(mimeMessage, mimeMessage.getAllRecipients());
+					Address[] addresses = mimeMessage.getAllRecipients();
+					transport.sendMessage(mimeMessage, (addresses != null ? addresses : new Address[0]));
 				}
 				catch (Exception ex) {
 					Object original = (originalMessages != null ? originalMessages[i] : mimeMessage);