Fehlermeldung bei Deinstallation des Chats

Fatal error: Could not execute prepared statement: SQLSTATE[42000]: Syntax error or access violation: 1091 Can't DROP 'f7e9a723f73b3d01a934e5e17fce9c83_fk'; check that column/key existsInformation:id: 58b3b663f0e382da4c56523b41c880e7873303f7
error message: Could not execute prepared statement: SQLSTATE[42000]: Syntax error or access violation: 1091 Can't DROP 'f7e9a723f73b3d01a934e5e17fce9c83_fk'; check that column/key exists
error code: 42000
sql type: wcf\system\database\MySQLDatabase
sql error: Can't DROP 'f7e9a723f73b3d01a934e5e17fce9c83_fk'; check that column/key exists
sql error number: 42000
sql version: 5.6.19-1~dotdeb.1-log
sql query: ALTER TABLE wcf1_user DROP FOREIGN KEY `f7e9a723f73b3d01a934e5e17fce9c83_fk`
file: /var/sites/smashlabs/public/wcf/lib/system/database/statement/PreparedStatement.class.php (100)
php version: 5.6.1-1~dotdeb.1
wcf version: 2.0.9 (Maelstrom)
date: Tue, 07 Oct 2014 16:15:32 +0000
request: /wcf/acp/index.php/UninstallPackage/?&
referer: http://www.smashlabs.de/wcf/acp/index.php/PackageList/?packageID=15&


Stacktrace:#0 /var/sites/smashlabs/public/wcf/lib/system/database/editor/MySQLDatabaseEditor.class.php(187): wcf\system\database\statement\PreparedStatement->execute()
#1 /var/sites/smashlabs/public/wcf/lib/system/package/plugin/SQLPackageInstallationPlugin.class.php(126): wcf\system\database\editor\MySQLDatabaseEditor->dropForeignKey('wcf1_user', 'f7e9a723f73b3d0...')
#2 /var/sites/smashlabs/public/wcf/lib/system/package/PackageUninstallationDispatcher.class.php(114): wcf\system\package\plugin\SQLPackageInstallationPlugin->uninstall()
#3 /var/sites/smashlabs/public/wcf/lib/system/package/PackageUninstallationDispatcher.class.php(63): wcf\system\package\PackageUninstallationDispatcher->executePIP(Array)
#4 /var/sites/smashlabs/public/wcf/lib/acp/action/UninstallPackageAction.class.php(106): wcf\system\package\PackageUninstallationDispatcher->uninstall('65f4b6a9')
#5 /var/sites/smashlabs/public/wcf/lib/action/AbstractDialogAction.class.php(70): wcf\acp\action\UninstallPackageAction->stepUninstall()
#6 /var/sites/smashlabs/public/wcf/lib/action/AbstractAction.class.php(49): wcf\action\AbstractDialogAction->execute()
#7 /var/sites/smashlabs/public/wcf/lib/system/request/Request.class.php(58): wcf\action\AbstractAction->__run()
#8 /var/sites/smashlabs/public/wcf/lib/system/request/RequestHandler.class.php(108): wcf\system\request\Request->execute()
#9 /var/sites/smashlabs/public/wcf/acp/index.php(10): wcf\system\request\RequestHandler->handle('wcf', true)
#10 {main}