Index: privatemsg.module
===================================================================
RCS file: /cvs/drupal-contrib/contributions/modules/privatemsg/privatemsg.module,v
retrieving revision 1.70.2.30.2.91.2.81
diff -u -p -r1.70.2.30.2.91.2.81 privatemsg.module
--- privatemsg.module	27 Oct 2009 11:31:34 -0000	1.70.2.30.2.91.2.81
+++ privatemsg.module	31 Oct 2009 12:14:33 -0000
@@ -1756,7 +1756,10 @@ function privatemsg_message_load_multipl
   $messages = array();
   while ($message = db_fetch_array($result)) {
     // Load author of message.
-    $message['author'] = user_load($message['author']);
+    if (!($message['author'] = user_load($message['author']))) {
+      // If the user does not exist, hide this message.
+      continue;
+    }
     $returned = module_invoke_all('privatemsg_message_load', $message);
     if (!empty($returned)) {
       $message = array_merge_recursive($returned, $message);
Index: privatemsg.test
===================================================================
RCS file: /cvs/drupal-contrib/contributions/modules/privatemsg/privatemsg.test,v
retrieving revision 1.2.2.6
diff -u -p -r1.2.2.6 privatemsg.test
--- privatemsg.test	27 Oct 2009 11:31:35 -0000	1.2.2.6
+++ privatemsg.test	31 Oct 2009 12:14:33 -0000
@@ -400,6 +400,16 @@ class PrivatemsgTestCase extends DrupalW
     $this->assertText($body1, 'First message is still displayed');
     $this->assertNoText($body2, 'Second message has been deleted for all users');
 
+    // Check that messages of deleted users are hidden.
+    $edit = array('body' => $this->randomName(100));
+    $this->drupalPost(NULL, $edit, t('Send message'));
+
+    $this->drupalLogin($admin);
+    $this->drupalGet('messages/view/' . $return['message']['thread_id']);
+    $this->assertText($edit['body'], t('New reply is displayed'));
+    user_delete(array(), $recipient2->uid);
+    $this->drupalGet('messages/view/' . $return['message']['thread_id']);
+    $this->assertNoText($edit['body'], t('Reply of deleted users is not displayed anymore'));
   }
 
   /**