Impossible to access an attribute on a boolean variable about linkit HOT 5 CLOSED

{% for block in blocks %}
    {% switch block.type %}
        {% case "singleImageBlock" %}
            {% set oneImage = block.image.first() %}
            {% set pixelWidth = (960 * (block.width/100))|round(0,'ceil') %}
            {% set thumb = {mode: 'fit', width: pixelWidth, quality: 75} %}
            <div class="singleImage {{block.alignment}}" style="width: {{block.width}}%">
                {% if block.optionalLink is defined %}
                    <a href="{{block.optionalLink.url}}" {{ block.optionalLink.target ? ' target="_blank"' }}><img src="{{ oneImage.url(thumb) }}" width="100%"/></a>
                {% else %}
                    <img src="{{ oneImage.url(thumb) }}" width="100%"/>
                {% endif %}
            </div>
    {% endswitch %}
{% endfor %}

<nav id="headerNav">
    <ul>
        {% for link in navigation.links %}
        <li><a href="{{ link.href.url }}" {{ link.href.target ? ' target="_blank"' }} {{link.href.url in craft.request.url and link.href.url != siteUrl ? 'class="active"' }} title="{{ link.href.linkText }}">{{ link.href.linkText }}</a></li>
        {% endfor %}
    </ul>
</nav>

{% switch entry.type %}
    {% case "blogLink" %}
        {% set blogLinkText = '"'~entry.blogFeatLink.url~'" class="blogExtLink" target="_blank"' %}
    {% endswitch %}
        <div class="blogPostMedSidebar">
            by {{entry.author.fullName}}<br />
            {{entry.postDate.format("F j, Y")}}
        </div>
        {% set blogNoLink = '"'~entry.url~'"' %}
        <div class="col-sm-22">
            <h1><a href={{ blogLinkText is defined ? blogLinkText|raw : blogNoLink|raw }}>{{entry.title}}</a></h1>
        </div>

{% if block.optionalLink is defined %}

{% if block.optionalLink is defined and block.optionalLink %}