Ticket #19366: 19366.patch

wp-includes/query.php

@@ -2683 +2683 @@
                                 }
                         }
 
-                        if ( $this->is_preview && current_user_can( $edit_cap, $this->posts[0]->ID ) )
+                        if ( $this->is_preview && !empty( $this->posts ) && current_user_can( $edit_cap, $this->posts[0]->ID ) )
                                 $this->posts[0] = apply_filters_ref_array('the_preview', array( $this->posts[0], &$this ));
                 }