Twig\Error\RuntimeError

Line 12 of /var/www/vhosts/musikschule-bregenzerwald.at/site/templates/event.twig

Impossible to invoke a method ("crop") on a null variable.

        {% if sliderItems|length > 0 %}
            <div class="swiper-container js-swiper">
                <div class="swiper-wrapper">
                {% for sliderItem in sliderItems %}
                    <div class="swiper-slide" data-caption="{{ sliderItem.caption }}">
                        {% set image = sliderItem.image.toFile() %}
                        {{ image.crop(650, 430)|raw }}
                    </div>
                {% endfor %}
                </div>
                <div class="swiper-footer">
                    <div class="swiper-pagination headline4"></div>
                    <div class="swiper-caption copySmall">{{ sliderItems.first().caption }}</div>