Index: Classes/Site/Entity/Site.php
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
--- Classes/Site/Entity/Site.php
+++ Classes/Site/Entity/Site.php
@@ -130,8 +130,8 @@
                 }
             }
             $this->languages[$languageUid] = new SiteLanguage(
-                $languageUid,
-                $languageConfiguration['locale'],
+                (int)$languageUid,
+               $languageConfiguration['locale'] ?? '',
                 $base,
                 $languageConfiguration
             );