How to assign a URL to only one slide in a template using Matrix?
Try something like:

{% for block in entry.information %}
{% if block.type == "images" %}
    {% set image = block.image.first() %}
        {% if image %}
            {% if block.anchor |length %}
            &lt;a href={{ block.anchor | cacheBuster }} target="_blank"&gt;
                &lt;img class="slideshow" src={{ image.url | cacheBuster }} alt={{ image.title }}&gt;
            &lt;/a&gt;
            {% else %}
            &lt;img class="slideshow" src={{ image.url | cacheBuster }} alt={{ image.title }}&gt;
            {% endif %}
        {% endif %}
    {% endif %}
{% endfor %}


So that only if the block.anchor field has something in it do you generate the link &amp; the image. Otherwise, you just generate the image.