bug symfony#25305 [Form][TwigBridge] Fix collision between view properties and form fields (yceruto)

This PR was merged into the 3.3 branch.

Discussion
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[Form][TwigBridge] Fix collision between view properties and form fields

| Q             | A
| ------------- | ---
| Branch?       | 3.3
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | -
| License       | MIT
| Doc PR        | -

Require symfony#25236 merged in 3.3

Commits
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888b48a Fix collision between view properties and form fields

Author: fabpot

src/Symfony/Bridge/Twig/Resources/views/Form/foundation_5_layout.html.twig

@@ -318,11 +318,11 @@
 
 {% block form_errors -%}
     {% if errors|length > 0 -%}
-        {% if form.parent %}<small class="error">{% else %}<div data-alert class="alert-box alert">{% endif %}
+        {% if form is not rootform %}<small class="error">{% else %}<div data-alert class="alert-box alert">{% endif %}
         {%- for error in errors -%}
             {{ error.message }}
             {% if not loop.last %}, {% endif %}
         {%- endfor -%}
-        {% if form.parent %}</small>{% else %}</div>{% endif %}
+        {% if form is not rootform %}</small>{% else %}</div>{% endif %}
     {%- endif %}
 {%- endblock form_errors %}