Do not setup appdata in constructor to avoid errors causing the whole instance to stop working

[juliusknorr]

This avoid having the whole instance going down in cases where there is something wrong with the documents folder.

Trace for occ failure, however the the reason for the wrong mimetype in filecache is still unclear

An unhandled exception has been thrown:
TypeError: Argument 1 passed to OC\Files\SimpleFS\SimpleFolder::__construct() must implement interface OCP\Files\Folder, instance of OC\Files\Node\File given, called in /var/www/nextcloud/lib/private/Files/AppData/AppData.php on line 151 and defined in /var/www/nextcloud/lib/private/Files/SimpleFS/SimpleFolder.php:42
Stack trace:
#0 /var/www/nextcloud/lib/private/Files/AppData/AppData.php(151): OC\Files\SimpleFS\SimpleFolder->__construct(Object(OC\Files\Node\File))
#1 /var/www/nextcloud/apps/text/lib/Service/DocumentService.php(112): OC\Files\AppData\AppData->getFolder('documents')
#2 [internal function]: OCA\Text\Service\DocumentService->__construct(Object(OCA\Text\Db\DocumentMapper), Object(OCA\Text\Db\StepMapper), Object(OC\Files\AppData\AppData), NULL, Object(OC\Files\Node\LazyRoot), Object(OC\Memcache\Factory), Object(OC\AppFramework\Logger), Object(OC\Share20\Manager), Object(OC\AppFramework\Http\Request), Object(OC\DirectEditing\Manager), Object(OC\Lock\MemcacheLockingProvider))
#3 /var/www/nextcloud/lib/private/AppFramework/Utility/SimpleContainer.php(83): ReflectionClass->newInstanceArgs(Array)
#4 /var/www/nextcloud/lib/private/AppFramework/Utility/SimpleContainer.php(100): OC\AppFramework\Utility\SimpleContainer->buildClass(Object(ReflectionClass))
#5 /var/www/nextcloud/lib/private/AppFramework/Utility/SimpleContainer.php(115): OC\AppFramework\Utility\SimpleContainer->resolve('OCA\\Text\\Servic...')
#6 /var/www/nextcloud/lib/private/AppFramework/DependencyInjection/DIContainer.php(415): OC\AppFramework\Utility\SimpleContainer->query('OCA\\Text\\Servic...')
#7 /var/www/nextcloud/lib/private/AppFramework/DependencyInjection/DIContainer.php(386): OC\AppFramework\DependencyInjection\DIContainer->queryNoFallback('OCA\\Text\\Servic...')
#8 /var/www/nextcloud/lib/private/AppFramework/Utility/SimpleContainer.php(70): OC\AppFramework\DependencyInjection\DIContainer->query('OCA\\Text\\Servic...', true)
#9 /var/www/nextcloud/lib/private/AppFramework/Utility/SimpleContainer.php(100): OC\AppFramework\Utility\SimpleContainer->buildClass(Object(ReflectionClass))
#10 /var/www/nextcloud/lib/private/AppFramework/Utility/SimpleContainer.php(115): OC\AppFramework\Utility\SimpleContainer->resolve('OCA\\Text\\Comman...')
#11 /var/www/nextcloud/lib/private/AppFramework/DependencyInjection/DIContainer.php(415): OC\AppFramework\Utility\SimpleContainer->query('OCA\\Text\\Comman...')
#12 /var/www/nextcloud/lib/private/ServerContainer.php(134): OC\AppFramework\DependencyInjection\DIContainer->queryNoFallback('OCA\\Text\\Comman...')
#13 /var/www/nextcloud/lib/private/Console/Application.php(220): OC\ServerContainer->query('OCA\\Text\\Comman...')
#14 /var/www/nextcloud/lib/private/Console/Application.php(135): OC\Console\Application->loadCommandsFromInfoXml(Array)
#15 /var/www/nextcloud/console.php(98): OC\Console\Application->loadCommands(Object(Symfony\Component\Console\Input\ArgvInput), Object(Symfony\Component\Console\Output\ConsoleOutput))
#16 /var/www/nextcloud/occ(11): require_once('/var/www/nextcl...')

[juliusknorr]

/backport to stable20

[juliusknorr]

/backport to stable19