do not render price if unknown

templates/index.html

@@ -3,6 +3,6 @@
 {%block body %}
     <h1>Recipes</h1>
     {% for recipe in recipes %}
-    <li>{{price(recipe)}} <a href="{{ recipe.outpath }}">{{ recipe.title }}</a></li>
+    <li>{% if recipe.price != None %}{{price(recipe.price)}} {%endif%}<a href="{{ recipe.outpath }}">{{ recipe.title }}</a></li>
     {% endfor %}
 {%endblock%}