Update WBB 4 -> WBB 4.1: "Update not supported"

An update of package com.woltlab.wcf from version 2.0.13 pl 1 to 2.1.0 Beta 2 is not supported.




Stacktrace:
#0 /var/www/html/wcf/lib/system/package/PackageInstallationScheduler.class.php(556): wcf\system\package\PackageInstallationScheduler->findShortestUpdateThread('com.woltlab.wcf', Array, '2.0.13 pl 1', '2.1.0 Beta 2')
#1 /var/www/html/wcf/lib/system/package/PackageInstallationScheduler.class.php(556): wcf\system\package\PackageInstallationScheduler->findShortestUpdateThread('com.woltlab.wcf', Array, '2.0.13 pl 1', '2.1.0 Beta 3')
#2 /var/www/html/wcf/lib/system/package/PackageInstallationScheduler.class.php(556): wcf\system\package\PackageInstallationScheduler->findShortestUpdateThread('com.woltlab.wcf', Array, '2.0.13 pl 1', '2.1.0 Beta 4')
#3 /var/www/html/wcf/lib/system/package/PackageInstallationScheduler.class.php(556): wcf\system\package\PackageInstallationScheduler->findShortestUpdateThread('com.woltlab.wcf', Array, '2.0.13 pl 1', '2.1.0 RC 1')
#4 /var/www/html/wcf/lib/system/package/PackageInstallationScheduler.class.php(556): wcf\system\package\PackageInstallationScheduler->findShortestUpdateThread('com.woltlab.wcf', Array, '2.0.13 pl 1', '2.1.0 RC 2')
#5 /var/www/html/wcf/lib/system/package/PackageInstallationScheduler.class.php(556): wcf\system\package\PackageInstallationScheduler->findShortestUpdateThread('com.woltlab.wcf', Array, '2.0.13 pl 1', '2.1.0')
#6 /var/www/html/wcf/lib/system/package/PackageInstallationScheduler.class.php(556): wcf\system\package\PackageInstallationScheduler->findShortestUpdateThread('com.woltlab.wcf', Array, '2.0.13 pl 1', '2.1.1')
#7 /var/www/html/wcf/lib/system/package/PackageInstallationScheduler.class.php(556): wcf\system\package\PackageInstallationScheduler->findShortestUpdateThread('com.woltlab.wcf', Array, '2.0.13 pl 1', '2.1.2')
#8 /var/www/html/wcf/lib/system/package/PackageInstallationScheduler.class.php(556): wcf\system\package\PackageInstallationScheduler->findShortestUpdateThread('com.woltlab.wcf', Array, '2.0.13 pl 1', '2.1.3')
#9 /var/www/html/wcf/lib/system/package/PackageInstallationScheduler.class.php(556): wcf\system\package\PackageInstallationScheduler->findShortestUpdateThread('com.woltlab.wcf', Array, '2.0.13 pl 1', '2.1.4')
#10 /var/www/html/wcf/lib/system/package/PackageInstallationScheduler.class.php(556): wcf\system\package\PackageInstallationScheduler->findShortestUpdateThread('com.woltlab.wcf', Array, '2.0.13 pl 1', '2.1.5')
#11 /var/www/html/wcf/lib/system/package/PackageInstallationScheduler.class.php(556): wcf\system\package\PackageInstallationScheduler->findShortestUpdateThread('com.woltlab.wcf', Array, '2.0.13 pl 1', '2.1.6')
#12 /var/www/html/wcf/lib/system/package/PackageInstallationScheduler.class.php(556): wcf\system\package\PackageInstallationScheduler->findShortestUpdateThread('com.woltlab.wcf', Array, '2.0.13 pl 1', '2.1.7')
#13 /var/www/html/wcf/lib/system/package/PackageInstallationScheduler.class.php(556): wcf\system\package\PackageInstallationScheduler->findShortestUpdateThread('com.woltlab.wcf', Array, '2.0.13 pl 1', '2.1.8')
#14 /var/www/html/wcf/lib/system/package/PackageInstallationScheduler.class.php(556): wcf\system\package\PackageInstallationScheduler->findShortestUpdateThread('com.woltlab.wcf', Array, '2.0.13 pl 1', '2.1.9')
#15 /var/www/html/wcf/lib/system/package/PackageInstallationScheduler.class.php(556): wcf\system\package\PackageInstallationScheduler->findShortestUpdateThread('com.woltlab.wcf', Array, '2.0.13 pl 1', '2.1.10')
#16 /var/www/html/wcf/lib/system/package/PackageInstallationScheduler.class.php(499): wcf\system\package\PackageInstallationScheduler->findShortestUpdateThread('com.woltlab.wcf', Array, '2.0.13 pl 1', '2.1.11 pl 1')
#17 /var/www/html/wcf/lib/system/package/PackageInstallationScheduler.class.php(191): wcf\system\package\PackageInstallationScheduler->updatePackage(1, '2.1.11')
#18 /var/www/html/wcf/lib/system/package/PackageInstallationScheduler.class.php(506): wcf\system\package\PackageInstallationScheduler->resolveRequirements('2251')
#19 /var/www/html/wcf/lib/system/package/PackageInstallationScheduler.class.php(102): wcf\system\package\PackageInstallationScheduler->updatePackage('4', '4.1.11')
#20 /var/www/html/wcf/lib/system/package/PackageInstallationScheduler.class.php(64): wcf\system\package\PackageInstallationScheduler->tryToInstallPackage('com.woltlab.wbb', '4.1.11', true)
#21 /var/www/html/wcf/lib/data/package/update/PackageUpdateAction.class.php(497): wcf\system\package\PackageInstallationScheduler->buildPackageInstallationStack()
#22 /var/www/html/wcf/lib/data/package/update/PackageUpdateAction.class.php(449): wcf\data\package\update\PackageUpdateAction->createQueue('update')
#23 [internal function]: wcf\data\package\update\PackageUpdateAction->prepareUpdate()
#24 /var/www/html/wcf/lib/data/AbstractDatabaseObjectAction.class.php(182): call_user_func(Array)
#25 /var/www/html/wcf/lib/action/AJAXProxyAction.class.php(76): wcf\data\AbstractDatabaseObjectAction->executeAction()
#26 /var/www/html/wcf/lib/action/AJAXInvokeAction.class.php(96): wcf\action\AJAXProxyAction->invoke()
#27 /var/www/html/wcf/lib/action/AbstractAction.class.php(49): wcf\action\AJAXInvokeAction->execute()
#28 /var/www/html/wcf/lib/action/AJAXInvokeAction.class.php(63): wcf\action\AbstractAction->__run()
#29 /var/www/html/wcf/lib/system/request/Request.class.php(58): wcf\action\AJAXInvokeAction->__run()
#30 /var/www/html/wcf/lib/system/request/RequestHandler.class.php(108): wcf\system\request\Request->execute()
#31 /var/www/html/acp/index.php(10): wcf\system\request\RequestHandler->handle('wbb', true)
#32 {main}