FIND:

if ( is_user_logged_in() ) {
                            $ln = 300; /*show first 300 characters*/
                            post::get_excerpt($post, $ln = $ln);
                        } else {
                            if ( !tools::is_nsfw( $post -> ID ) ) {
                                the_excerpt();
                            }else{
                                echo '<p>' . options::get_value( 'general' , 'nsfw_content' ) . '</p>';
                            }
                        }


CHANGE IN:

if ( is_user_logged_in() ) {
                            $ln = 300; /*show first 300 characters*/
                            post::get_excerpt($post, $ln = $ln);
                        } else {
                            if ( !tools::is_nsfw( $post -> ID ) ) {
                                post::get_excerpt($post, $ln = $ln);
                            }else{
                                echo '<p>' . options::get_value( 'general' , 'nsfw_content' ) . '</p>';
                            }
                        }