public function render()
    {
        if (!$this->visible) {
            return;
        }

        $is_null = $this->strict ? $this->text === null : $this->text == null;

        if ($is_null) {
            $this->text = $this->null_text;

            echo '<span class="swat-null-text-cell-renderer">';
            parent::render();
            echo '</span>';

            // Reset the text so that subsequent $is_null checks pass.
            $this->text = null;
        } else {
            parent::render();
        }
    }