Otherwise a fatal PHP error is thrown since the filesystem is not setup:
```
( ! ) Fatal error: Call to a member function getOwner() on null in /Users/lreschke/Programming/core/lib/private/files/filesystem.php on line 817
Call Stack
1 0.0004 247792 {main}( ) ../index.php:0
2 0.0946 5088776 OC::handleRequest( ) ../index.php:28
3 0.1423 7491280 OC\Route\Router->match( ) ../base.php:748
4 0.1664 8592152 call_user_func:{/Users/lreschke/Programming/core/lib/private/route/router.php:250} ( ) ../router.php:250
5 0.1664 8592216 __lambda_func( ) ../router.php:250
6 0.1665 8599064 require_once( '/Users/lreschke/Programming/core/apps/files_versions/ajax/getVersions.php' ) ../route.php(135) : runtime-created function:1
7 0.1801 9061096 OCA\Files_Versions\Storage::getUidAndFilename( ) ../getVersions.php:7
8 0.1801 9061144 OC\Files\Filesystem::getOwner( ) ../storage.php:45
```
Furthermore this adds the CSRF check as a nice-to-have addition, the requests accessing this are done via the jQuery AJAX methods and thus the header is automatically added to all requests already.
Added addTranslations and fixed de.js file
Fixed de.js to use OC.L10N.register() and use to correct expected
format.
Added JS unit tests for OC.L10N class
Include translations JS script for all apps
filter installed and not-installed apps properly
kill unneeded file
load category 'Installed' on page load
adding documentation links
new apps mgmt: first style adjustment
apps mgmt: only show license and preview if they exist
adding buttons
new apps mgmt: fix for mobile
use app icon if available
new apps mgmt: position enable/disable toggle to the right
new apps mgmt: proper display of icons or previews
new apps mgmt: fix loading spinner
reenable group selection for apps
new apps mgmt: position enable button normally again
new apps mgmt: clarify wording from 'Installed' to 'Enabled'
reintroduce enable/disable
Move rating image path generation to client-side
Move expression outside of l10n
fix group handling
add buttons for 'More apps' and 'Add your app' again
disable changed date of app for now
adding recommended label
style 'Recommended' app tag
fixing php warning
sort by rating
adding meta-category 'Recommended'
Only show existing documentation links
lacy loading of screenshots
making group based app activation work again
adding support to get the app icon not only by the app name but also simply by the fixed name 'app.svg'
adding app.svg for all core apps
query string '?installed' is not longer needed
update and uninstall is back + error feedback
remove unneeded parameter
fix alignment of 'recommended' label
