Fix fallbacks for variables

templates/base.html

@@ -85,7 +85,7 @@
     <main role="main">
     <!-- Main Content -->
 	{% block content %}{% endblock %}
-	<p class="licence">{{ LICENCETEXTS[article.lang or DEFAULT_LANG] }} {{ article.metadata.licence or LICENCE_DEFAULT }}.</p>
+	<p class="licence">{{ LICENCETEXTS[article.lang|default:DEFAULT_LANG] }} {{ article.metadata.licence|default:LICENCE_DEFAULT }}.</p>
     </main>
 
     <!-- Sponsoren-Footer -->
@@ -96,7 +96,7 @@
             <div class="row">
                 <div class="col s12">
                     <h3 id='sponsorheading' class="black-text">Sponsoren</h3>
-		    <p id="sponsortext" class="black-text">{% block sponsorstext %}{{ SPONSORSTEXTS[article.lang or DEFAULT_LANG] }}{% endblock %}</p>
+		    <p id="sponsortext" class="black-text">{% block sponsorstext %}{{ SPONSORSTEXTS[article.lang|default:DEFAULT_LANG] }}{% endblock %}</p>
                     {% for image, url in SPONSOR_LOGOS %}
                         <a href="{{ url }}"><img src="{{ image }}" href="{{ url }}" alt="{{ url }}" class="sponsorslogo" /></a>
                     {% endfor %}