Fixed #17829

Author: brandonkelly

CHANGELOG.md

@@ -14,6 +14,7 @@
 - Fixed a bug where non-admin users couldn’t edit recursively-nested elements if they didn’t have save permissions for the top-level element.
 - Fixed a bug where it was possible to select disabled elements within element select modals. ([#17824](https://github.com/craftcms/cms/issues/17824))
 - Fixed a bug where toast notifications weren’t always being dismissed automatically when they should have. ([#17825](https://github.com/craftcms/cms/issues/17825))
+- Fixed an error that could occur if a Content Block field was saved without any fields selected. ([#17829](https://github.com/craftcms/cms/issues/17829))
 - Fixed a styling issue.
 
 ## 5.8.16 - 2025-08-29

src/fields/ContentBlock.php

@@ -260,7 +260,7 @@ public function setFieldLayout(FieldLayout|array|string $layout): void
     public function setFieldLayouts(array $layouts): void
     {
         $config = reset($layouts);
-        $layout = Craft::$app->getFields()->createLayout($config);
+        $layout = Craft::$app->getFields()->createLayout($config ?: []);
         $layout->uid = array_key_first($layouts);
         $layout->type = ContentBlockElement::class;