It's an API broker and an uneeded system : imageSrc return false for invalid image : it's clean , return ERROR : really not clean.

        {# Logo option #}
        {% if( aSurveyInfo.options.brandlogo == "on" or imageSrc("upload/surveys/"~processString("{SID}")~"/images/logo.png") ) %}
            <div class="{{ aSurveyInfo.class.navbarbrand }} logo-container hidden-xs"  {{ aSurveyInfo.attr.navbarbrand }}  >
                {% if(imageSrc("upload/surveys/"~processString("{SID}")~"/images/logo.png") ) %}
                    {{ image("upload/surveys/"~processString("{SID}")~"/images/logo.png", aSurveyInfo.name, {"class": "logo img-responsive"}) }}
                {% else %}
                  {{ image(aSurveyInfo.options.brandlogofile, aSurveyInfo.name, {"class": "logo img-responsive"}) }}
                {% endif %}
            </div>
        {% else %}
            <div class="{{ aSurveyInfo.class.navbarbrand }}"  {{ aSurveyInfo.attr.navbarbrand }} >
                {{ aSurveyInfo.name }}
            </div>
        {% endif %}