TYPO3 Core

Hi,

I did some tests with the scheduler and wrote 2 custom extensions, registered a class, created a task for it and deactivated the extensions in extension manager.

now scheduler won't work anymore! complete error is
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Fatal error: tx_scheduler_Module::listTasks() [<a href='tx-scheduler-module.listtasks'>tx-scheduler-module.listtasks</a>]: The script tried to execute a method or access a property of an incomplete object. Please ensure that the class definition "tx_check4exts_server" of the object you are trying to operate on was loaded before unserialize() gets called or provide a __autoload() function to load the class definition in /html/typo3/sysext/scheduler/mod1/index.php on line 889
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if I delete the tasks and deactivate the extension afterwards, everything is fine but IMO this needs to be fixed!

(issue imported from #M12132)