[BUGFIX] Catch FolderDoesNotExistException in getCurrentFolder

[mikelwohlschlegel]

When a folder is selected and then deleted via context menu, the page reloads with the deleted folder's ID still in the query parameters. getCurrentFolder() tries to resolve this non-existent folder and throws FolderDoesNotExistException.

Fall back to the root level folder when the requested folder no longer exists.

Steps to reproduce

1. Navigate to the Filelist module in the TYPO3 backend
2. Click on a folder to select it (e.g. user_upload/test/) — this sets the id query parameter in the URL
3. Right-click the selected folder to open the context menu
4. Choose Delete and confirm the deletion
5. The page reloads with the deleted folder's ID still in the URL → exception is thrown

[helhum]

Thanks @mikelwohlschlegel

While I would argue that this is a TYPO3 bug as well, it totally makes sense to fix it here.

[helhum]

Released as 3.1.3