[Form][WebProfiler] Empty form names fix

When a Form had no name, the markup was broken in the profiler,
making the form tree ugly.

src/Symfony/Bundle/WebProfilerBundle/Resources/views/Collector/form.html.twig

@@ -420,7 +420,7 @@
             {% else %}
                 <div class="toggle-icon empty"></div>
             {% endif %}
-            {{ name }}
+            {{ name|default('(no name)') }}
             {% if data.errors is defined and data.errors|length > 0 %}
             <div class="badge-error">{{ data.errors|length }}</div>
             {% endif %}