This function is also used in a way such as:

```
	$preview = new \OC\Preview(\OC_User::getUser(), 'files');
	$info = \OC\Files\Filesystem::getFileInfo($file);
	if (!$always and !$preview->isAvailable($info)) {
		\OC_Response::setStatus(404);
	} else {
		$preview->setFile($file);
		$preview->setMaxX($maxX);
		$preview->setMaxY($maxY);
		$preview->setScalingUp($scalingUp);
		$preview->setKeepAspect($keepAspect);
	}
```

Which won't work anymore since `setFile` is used instead of passing the file in the constructor. Fixes a regression in master.

Ref https://github.com/owncloud/core/issues/11078

2. use count instead of sizeof. Latter is an alias to first one, practically we stick to count everywhere. Having it consistent helps with readability.
3. move whitespace so we have $groupUsers[] = $filteredUser; instead of $groupUsers []= $filteredUser;

Ensures that Basic Auth works properly for APIs and removes the need for some even uglier lines of code.

Resolves https://github.com/owncloud/core/issues/10991 failure 4

Fixes https://github.com/owncloud/core/issues/11133

We do not support updates from 6 to 8 directly, therefore we can remove those upgrade routines.

Thumbnail generation

Removed Log

Added requested changes

Added requested changes.

- Fix code style
- Add exception if file does not exist
- Switch route styling

Replaces https://github.com/owncloud/core/pull/10805

Fix codestyle

Fix codestyle

Migrate to appframework

Fix typo

Some code that I also used for https://github.com/owncloud/administration/pull/11

if dbuser exists try a different one, owncloud/core#108

changed outdated comment

corrected length calculation

changed indentation for else clauses

You can't add int here as hint...

Conflicts:
	core/templates/layout.guest.php

Step one, open guest layout for different styles.

Fixes https://github.com/owncloud/core/issues/11004

Fix #7148 - again :)