see below stack trace

ERROR [2022-10-24 02:05:15] 2060 Uncaught exception in API: Exception: User 'MyUsername' doesn't exist. in plugins/UsersManager/API.php:1303
Stack trace:
#0 plugins/UsersManager/API.php(677): Piwik\Plugins\UsersManager\API->checkUserExists('MyUsername')
#1 [internal function]: Piwik\Plugins\UsersManager\API->getUser('MyUsername')
#2 core/API/Proxy.php(244): call_user_func_array(Array, Array)
#3 core/Context.php(28): Piwik\API\Proxy->Piwik\API{closure}()
#4 core/API/Proxy.php(335): Piwik\Context::executeWithQueryParameters(Array, Object(Closure))
#5 core/API/Request.php(267): Piwik\API\Proxy->call('\Piwik\Plugins\...', 'getUser', Array)
#6 core/API/Request.php(560): Piwik\API\Request->process()
#7 plugins/CoreAdminHome/Tasks.php(165): Piwik\API\Request::processRequest('UsersManager.ge...', Array)
#8 [internal function]: Piwik\Plugins\CoreAdminHome\Tasks->checkSiteHasTrackedVisits('3')
#9 core/Scheduler/Scheduler.php(309): call_user_func(Array, '3')
#10 core/Scheduler/Scheduler.php(154): Piwik\Scheduler\Scheduler->executeTask(Object(Piwik\Scheduler\Task))
#11 plugins/CoreAdminHome/API.php(75): Piwik\Scheduler\Scheduler->run()
#12 core/CronArchive.php(653): Piwik\Plugins\CoreAdminHome\API->runScheduledTasks()
#13 core/CronArchive.php(279): Piwik\CronArchive->runScheduledTasks()
#14 core/Access.php(661): Piwik\CronArchive->Piwik{closure}()
#15 core/CronArchive.php(284): Piwik\Access::doAsSuperUser(Object(Closure))
#16 plugins/CoreConsole/Commands/CoreArchiver.php(32): Piwik\CronArchive->main()
#17 vendor/symfony/console/Symfony/Component/Console/Command/Command.php(257): Piwik\Plugins\CoreConsole\Commands\CoreArchiver->execute(Object(Symfony\Component\Console\Input\ArgvInput), Object(Symfony\Component\Console\Output\ConsoleOutput))
#18 vendor/symfony/console/Symfony/Component/Console/Application.php(874): Symfony\Component\Console\Command\Command->run(Object(Symfony\Component\Console\Input\ArgvInput), Object(Symfony\Component\Console\Output\ConsoleOutput))
#19 vendor/symfony/console/Symfony/Component/Console/Application.php(195): Symfony\Component\Console\Application->doRunCommand(Object(Piwik\Plugins\CoreConsole\Commands\CoreArchiver), Object(Symfony\Component\Console\Input\ArgvInput), Object(Symfony\Component\Console\Output\ConsoleOutput))
#20 [internal function]: Symfony\Component\Console\Application->doRun(Object(Symfony\Component\Console\Input\ArgvInput), Object(Symfony\Component\Console\Output\ConsoleOutput))
#21 core/Console.php(135): call_user_func(Array, Object(Symfony\Component\Console\Input\ArgvInput), Object(Symfony\Component\Console\Output\ConsoleOutput))
#22 core/Access.php(670): Piwik\Console->Piwik{closure}()
#23 core/Console.php(136): Piwik\Access::doAsSuperUser(Object(Closure))
#24 core/Console.php(87): Piwik\Console->doRunImpl(Object(Symfony\Component\Console\Input\ArgvInput), Object(Symfony\Component\Console\Output\ConsoleOutput))
#25 vendor/symfony/console/Symfony/Component/Console/Application.php(126): Piwik\Console->doRun(Object(Symfony\Component\Console\Input\ArgvInput), Object(Symfony\Component\Console\Output\ConsoleOutput))
#26 console(32): Symfony\Component\Console\Application->run()
#27 {main}
ERROR [2022-10-24 02:05:15] 2060 Scheduler: Error User 'MyUsername' doesn't exist. for task 'Piwik\Plugins\CoreAdminHome\Tasks.checkSiteHasTrackedVisits_3'

Expected:

Error is caught in https://github.com/matomo-org/matomo/blob/4.12.2/plugins/CoreAdminHome/Tasks.php#L164-L169 as we would otherwise just return anyway if email not found