Fix searching language category in language file via GUI

See #2545

diff --git a/wcfsetup/install/files/lib/system/package/plugin/LanguagePackageInstallationPlugin.class.php b/wcfsetup/install/files/lib/system/package/plugin/LanguagePackageInstallationPlugin.class.php
index 21552c0d358203460fbe8ab7e210a73d1a874d04..7f6c809ac5c11f2cbe9263e50ef1068059ef0df8 100644 (file)
--- a/wcfsetup/install/files/lib/system/package/plugin/LanguagePackageInstallationPlugin.class.php
+++ b/wcfsetup/install/files/lib/system/package/plugin/LanguagePackageInstallationPlugin.class.php
@@ -772,7 +772,7 @@ XML;
                
                /** @var \DOMElement $languageCategory */
                foreach ($document->documentElement->childNodes as $languageCategory) {
-                       if ($languageCategory->getAttribute('name') === $languageCategoryName) {
+                       if ($languageCategory instanceof \DOMElement && $languageCategory->getAttribute('name') === $languageCategoryName) {
                                $languageCategory->appendChild($languageItem);
                                break;
                        }