[BootstrapAdminUi] Fix defining default value in twig templates

Author: loic425

compose.override.yaml

@@ -2,5 +2,5 @@ services:
 ###> doctrine/doctrine-bundle ###
   database:
     ports:
-      - "5432:5432"
+      - "5432"
 ###< doctrine/doctrine-bundle ###

src/BootstrapAdminUi/templates/shared/grid/action/create.html.twig

@@ -6,6 +6,6 @@
 {% endif %}
 
 <a href="{{ path }}" class="btn">
-    {{ ux_icon(action.icon ?? 'tabler:plus', {'class': 'icon dropdown-item-icon'}) }}
+    {{ ux_icon(action.icon|default('tabler:plus'), {'class': 'icon dropdown-item-icon'}) }}
     {{ message|trans }}
 </a>