FIX Set RelatedPages gridfield to be structural

src/PageTypes/BasePage.php

@@ -17,6 +17,7 @@
 use Symbiote\GridFieldExtensions\GridFieldOrderableRows;
 use TractorCow\Fluent\Model\Locale;
 use TractorCow\Fluent\State\FluentState;
+use SilverStripe\Forms\FormField;
 
 /**
  * `BasePage` is a foundation page class which can be used for constructing your own page types. By default it is
@@ -129,12 +130,16 @@ public function getCMSFields()
             );
             $fields->addFieldToTab(
                 'Root.RelatedPages',
-                GridField::create(
+                // Use an anonymous class to set $schemaDataType so that this field
+                // does not throw an exception in a react context e.g. versioned-admin
+                new class (
                     'RelatedPages',
                     _t(__CLASS__ . '.RelatedPages', 'Related pages'),
                     $this->RelatedPagesThrough(),
                     $components
-                )
+                ) extends GridField {
+                    protected $schemaDataType = FormField::SCHEMA_DATA_TYPE_STRUCTURAL;
+                }
             );
 
             // Taxonomies - Unless they have their own 'Tags' field (such as in Blog, etc)