update delete button in /user/pages.html template (incorrect value).

templates/user/pages.html

@@ -10,7 +10,7 @@
   {% if roles.administrator %}
   <form action="/page/delete" method="post">
     <input required type="hidden" name="AUTHENTICITY-TOKEN" value="{{token}}">
-    <input required type="hidden" name="slug" value="{{page}}">
+    <input required type="hidden" name="slug" value="{{page.slug}}">
     <input type="submit" value="Delete">
   </form>
   {% endif %}