Make source_url and issues_url optional and adapt content if not set

templates/404.html

@@ -8,10 +8,12 @@
 
 <h1>Page Not Found</h1>
 
-<p>The requested page could not be found. If you feel this is not normal, then you can create an issue on the issue tracker.</p>
+<p>The requested page could not be found.{% if config.extra.issues_url %} If you feel this is not normal, then you can create an issue on the issue tracker.{% endif %}</p>
 
 <p class="dialog-buttons">
 	<a onclick="window.history.go(-1)" class="inline-button">Go Back</a>
+	{% if config.extra.issues_url %}
 		<a class="inline-button colored" href="{{ config.extra.issues_url }}">File an Issue</a>
+	{% endif %}
 </p>
 {% endblock content %}

templates/article.html

@@ -105,6 +105,8 @@
 
 <p class="dialog-buttons">
 	<a class="inline-button" href="#top">Go to Top</a>
+	{% if config.extra.issues_url %}
 		<a class="inline-button colored" href="{{ config.extra.issues_url }}">File an Issue</a>
+	{% endif %}
 </p>
 {% endblock content %}

templates/partials/footer.html

@@ -21,7 +21,7 @@
 		<p title="Last built at {{ now() | date(format='%F %a %R') }}">&copy; {{ config.title }}, {{ now() | date(format="%Y") }}</p>
 	{% endif %}
 
-	{% if config.extra.footer.show_source %}
+	{% if config.extra.source_url and config.extra.footer.show_source %}
 		<p>
 			<a href="{{ config.extra.source_url | safe }}">Website source</a>
 		</p>