Fix content type pre save

src/CustomQueriesExtension.php

@@ -32,7 +32,7 @@ class CustomQueriesExtension extends SimpleExtension
         $subject = $event->getSubject();
         /** @var \Bolt\Storage\Mapping\ContentType $contentType */
         $contentType = $subject->getContentType();
-        if ($contentType){
+        if ($contentType && $contentType instanceof \Bolt\Storage\Mapping\ContentType){
             $fields = $contentType->getFields();
 
             $customQueryFields = [];