performance: use .exists to check for non empty queryset

panikweb_templates/templates/emissions/emission_detail.html

@@ -8,7 +8,7 @@
 	{% emission_nav %}
 {% endblock %}
 {% block main %}
-<div class="wrapper {% if episodes %}sided{% endif %} cf">
+<div class="wrapper {% if episodes.exists %}sided{% endif %} cf">
 	<div id="Emission-container" class="emission padded">
 		<div data-tabbed="true" id="Emission-tabs-default">
 			<div id="Emission-tabs-detail" class="leftPart">
@@ -46,7 +46,7 @@
 						{% endfor %}
 					</div>
 				{% endif %}
-				{% if episodes %}
+				{% if episodes.exists %}
 					<div class="sub">
 						<h5 class="sectionLabel">Dernier épisode</h5>
 						{% with episodes|slice:"0:1" as episodes %}

panikweb_templates/templates/emissions/nav.html

@@ -55,7 +55,7 @@
 		</header>
 </div>
 <div class="wrapper">
-	{% if episodes %}
+	{% if episodes.exists %}
 	<div class="wrapper half">
 		<nav>
 			<ul class="distributed by2">