=== modified file 'modules/comment/comment.module'
--- modules/comment/comment.module	
+++ modules/comment/comment.module	
@@ -173,9 +173,10 @@ function comment_block($op = 'list', $de
     return $blocks;
   }
   else if ($op == 'view' && user_access('access comments')) {
-    $block['subject'] = t('Recent comments');
-    $block['content'] = theme('comment_block');
-    return $block;
+    if ($block['content'] = theme('comment_block')) {
+      $block['subject'] = t('Recent comments');
+      return $block;
+    }
   }
 }
 
@@ -185,7 +186,9 @@ function theme_comment_block() {
   while ($comment = db_fetch_object($result)) {
     $items[] = l($comment->subject, 'node/'. $comment->nid, NULL, NULL, 'comment-'. $comment->cid) .'<br />'. t('@time ago', array('@time' => format_interval(time() - $comment->timestamp)));
   }
-  return theme('item_list', $items);
+  if ($items) {
+    return theme('item_list', $items);
+  }
 }
 
 /**