Fixed undefined variable in base_show.html.twig (#4527)

Resources/views/CRUD/base_show.html.twig

@@ -44,7 +44,7 @@ file that was distributed with this source code.
                         <li{% if loop.first %} class="active"{% endif %}>
                             <a href="#tab_{{ admin.uniqid }}_{{ loop.index }}" data-toggle="tab">
                                 <i class="fa fa-exclamation-circle has-errors hide" aria-hidden="true"></i>
-                                {{ view_group.label|trans({}, show_tab.translation_domain ?: admin.translationDomain) }}
+                                {{ show_tab.label|trans({}, show_tab.translation_domain ?: admin.translationDomain) }}
                             </a>
                         </li>
                     {% endfor %}