Check if the session exists before reading flash messages

Author: javiereguiluz

app/Resources/views/default/_flash_messages.html.twig

@@ -1,12 +1,14 @@
-<div class="messages">
-    {% for message in app.session.flashBag.get('success') %}
-        {# Bootstrap alert, see http://getbootstrap.com/components/#alerts #}
-        <div class="alert alert-dismissible alert-success" role="alert">
-            <button type="button" class="close" data-dismiss="alert" aria-label="Close">
-                <span aria-hidden="true">&times;</span>
-            </button>
+{% if app.session.started %}
+    <div class="messages">
+        {% for message in app.session.flashBag.get('success') %}
+            {# Bootstrap alert, see http://getbootstrap.com/components/#alerts #}
+            <div class="alert alert-dismissible alert-success" role="alert">
+                <button type="button" class="close" data-dismiss="alert" aria-label="Close">
+                    <span aria-hidden="true">&times;</span>
+                </button>
 
-            {{ message|trans }}
-        </div>
-    {% endfor %}
-</div>
+                {{ message|trans }}
+            </div>
+        {% endfor %}
+    </div>
+{% endif %}