diff --git a/core/modules/comment/comment.module b/core/modules/comment/comment.module
index 9ad7cfc..9c7f843 100644
--- a/core/modules/comment/comment.module
+++ b/core/modules/comment/comment.module
@@ -755,10 +755,12 @@ function comment_node_page_additions($node) {
     $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;
+      }
     }
   }
 
@@ -1375,9 +1377,11 @@ function comment_node_update_index($node) {
     $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 '';
diff --git a/core/modules/comment/comment.test b/core/modules/comment/comment.test
index 74f735d..b6e2615 100644
--- a/core/modules/comment/comment.test
+++ b/core/modules/comment/comment.test
@@ -2117,3 +2117,57 @@ class CommentFieldsTest extends CommentHelperCase {
     $this->drupalPost('node/' . $this->node->nid, $edit, t('Save'));
   }
 }
+
+/**
+ * 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.'));
+  }
+}