Do not use UNIQUE KEY, as the value null can be included

Author: Cyperghost

wcfsetup/install/files/acp/database/update_com.woltlab.wcf_6.2_step1.php

@@ -73,7 +73,6 @@
             DatabaseTablePrimaryIndex::create()
                 ->columns(['contentID']),
             DatabaseTableIndex::create('id')
-                ->type(DatabaseTableIndex::UNIQUE_TYPE)
                 ->columns(['rankID', 'languageID']),
         ])
         ->foreignKeys([

wcfsetup/setup/db/install.sql

@@ -1966,7 +1966,7 @@ CREATE TABLE wcf1_user_rank_content (
 	title VARCHAR(255) NOT NULL,
 
 	PRIMARY KEY(contentID),
-	UNIQUE KEY id (rankID, languageID)
+	KEY id (rankID, languageID)
 );
 
 DROP TABLE IF EXISTS wcf1_user_session;