Added missing namespace

diff --git a/wcfsetup/install/files/lib/acp/form/AbstractOptionListForm.class.php b/wcfsetup/install/files/lib/acp/form/AbstractOptionListForm.class.php
index 501959d7ae9758a87fd2452b885bc05774c215b0..28377df16b00f00e1690021507d07c0add560916 100755 (executable)
--- a/wcfsetup/install/files/lib/acp/form/AbstractOptionListForm.class.php
+++ b/wcfsetup/install/files/lib/acp/form/AbstractOptionListForm.class.php
@@ -7,6 +7,7 @@ use wcf\system\cache\CacheHandler;
 use wcf\system\exception\SystemException;
 use wcf\system\exception\UserInputException;
 use wcf\util\ClassUtil;
+use wcf\util\StringUtil;
 
 /**
  * This class provides default implementations for a list of options.