Add d-block to bootstrap 4 alerts

Author: Normunds

Resources/views/Form/bootstrap_4_layout.html.twig

@@ -267,7 +267,7 @@
 
 {% block form_errors -%}
     {%- if errors|length > 0 -%}
-        <span class="{% if form is not rootform %}invalid-feedback d-block{% else %}alert alert-danger{% endif %}">
+        <span class="{% if form is not rootform %}invalid-feedback d-block{% else %}alert alert-danger d-block{% endif %}">
             {%- for error in errors -%}
                 <span class="mb-0 d-block">
                     <span class="initialism form-error-icon badge badge-danger">{{ 'Error'|trans({}, 'validators') }}</span> <span class="form-error-message">{{ error.message }}</span>