reverted:
--- b/modules/comment/comment.module
+++ a/modules/comment/comment.module
@@ -730,12 +730,10 @@
     $comments_per_page = variable_get('comment_default_per_page_' . $node->type, 50);
     if ($cids = comment_get_thread($node, $mode, $comments_per_page)) {
       $comments = comment_load_multiple($cids);
+      comment_prepare_thread($comments);
+      $build = comment_view_multiple($comments, $node);
+      $build['pager']['#theme'] = 'pager';
+      $additions['comments'] = $build;
-      if ($comments) {
-        comment_prepare_thread($comments);
-        $build = comment_view_multiple($comments, $node);
-        $build['pager']['#theme'] = 'pager';
-        $additions['comments'] = $build;
-      }
     }
   }
 
@@ -1358,11 +1356,9 @@
     $comments_per_page = variable_get('comment_default_per_page_' . $node->type, 50);
     if ($node->comment && $cids = comment_get_thread($node, $mode, $comments_per_page)) {
       $comments = comment_load_multiple($cids);
+      comment_prepare_thread($comments);
+      $build = comment_view_multiple($comments, $node);
+      return drupal_render($build);
-      if ($comments) {
-        comment_prepare_thread($comments);
-        $build = comment_view_multiple($comments, $node);
-        return drupal_render($build);
-      }
     }
   }
   return '';
reverted:
--- b/modules/comment/comment.test
+++ a/modules/comment/comment.test
@@ -2223,57 +2223,3 @@
     $this->assertFalse(comment_load($comment->id), 'The comment could not be loaded after the node was deleted.');
   }
 }
-
-/**
- * Tests the behavior of comments when the comment author is deleted.
- */
-class CommentAuthorDeletionTestCase extends CommentHelperCase {
-  public static function getInfo() {
-    return array(
-      'name' => 'Comment author deletion',
-      'description' => 'Test the behavior of comments when the comment author is deleted.',
-      'group' => 'Comment',
-    );
-  }
-
-  /**
-   * Tests that comments are correctly deleted when their author is deleted.
-   */
-  function testAuthorDeletion() {
-    // Create a comment as the admin user.
-    $this->drupalLogin($this->admin_user);
-    $comment = $this->postComment($this->node, $this->randomName());
-    $this->assertTrue($this->commentExists($comment), t('Comment is displayed initially.'));
-    $this->drupalLogout();
-
-    // Delete the admin user, and check that the node which displays the
-    // comment can still be viewed, but the comment itself does not appear
-    // there.
-    user_delete($this->admin_user->uid);
-    $this->drupalGet('node/' . $this->node->nid);
-    $this->assertResponse(200, t('Node page is accessible after the comment author is deleted.'));
-    $this->assertFalse($this->commentExists($comment), t('Comment is not displayed after the comment author is deleted.'));
-  }
-
-  /**
-   * Test comment author deletion while the comment module is disabled.
-   */
-  function testAuthorDeletionCommentModuleDisabled() {
-    // Create a comment as the admin user.
-    $this->drupalLogin($this->admin_user);
-    $comment = $this->postComment($this->node, $this->randomName());
-    $this->assertTrue($this->commentExists($comment), t('Comment is displayed initially.'));
-    $this->drupalLogout();
-
-    // Delete the admin user while the comment module is disabled, and ensure
-    // that the missing comment author is still handled correctly (the node
-    // itself should be displayed, but the comment should not be displayed on
-    // it).
-    module_disable(array('comment'));
-    user_delete($this->admin_user->uid);
-    module_enable(array('comment'));
-    $this->drupalGet('node/' . $this->node->nid);
-    $this->assertResponse(200, t('Node page is accessible after the comment author is deleted.'));
-    $this->assertFalse($this->commentExists($comment), t('Comment is not displayed after the comment author is deleted.'));
-  }
-}
only in patch2:
unchanged:
--- a/core/modules/comment/comment.module
+++ b/core/modules/comment/comment.module
@@ -910,7 +910,12 @@ function comment_node_update_index(EntityInterface $node, $langcode) {
       $comments_per_page = $field_definition->getSetting('per_page');
       if ($node->get($field_name)->status && $cids = comment_get_thread($node, $field_name, $mode, $comments_per_page)) {
         $comments = entity_load_multiple('comment', $cids);
+      if ($comments) {
         comment_prepare_thread($comments);
+        $build = comment_view_multiple($comments, $node);
+        $build['pager']['#theme'] = 'pager';
+        $additions['comments'] = $build;
+      }
         $build = comment_view_multiple($comments);
         $return .= drupal_render($build);
       }