chore: safely eliminate future 8.4 deprecation warning

RFC: https://wiki.php.net/rfc/deprecate-implicitly-nullable-types
Proposed fix: `?T`
Can be auto-fixed with `PHP_CodeSniffer` using the sniff `SlevomatCodingStandard.TypeHints.NullableTypeForNullDefaultValue`
A TOTAL OF 281 ERRORS WERE FIXED IN 172 FILES

I manually reviewed each change.

Author: afilina

apps/comments/lib/Dav/EntityCollection.php

@@ -128,7 +128,7 @@ public function getChildren() {
 	 * @param \DateTime|null $datetime
 	 * @return CommentNode[]
 	 */
-	public function findChildren($limit = 0, $offset = 0, \DateTime $datetime = null) {
+	public function findChildren($limit = 0, $offset = 0, ?\DateTime $datetime = null) {
 		$comments = $this->commentsManager->getForObject($this->name, $this->id, $limit, $offset, $datetime);
 		$result = [];
 		foreach ($comments as $comment) {

apps/dav/lib/CardDAV/CardDavBackend.php

@@ -85,7 +85,7 @@ public function __construct(
 		IDBConnection $db,
 		Principal $principalBackend,
 		GroupPrincipalBackend $groupPrincipalBackend,
-		EventDispatcherInterface $dispatcher = null,
+		?EventDispatcherInterface $dispatcher = null,
 		$legacyMode = false
 	) {
 		$this->db = $db;

apps/dav/lib/CardDAV/SyncService.php

@@ -290,7 +290,7 @@ public function getLocalSystemAddressBook() {
 		return $this->localSystemAddressBook;
 	}
 
-	public function syncInstance(\Closure $progressCallback = null) {
+	public function syncInstance(?\Closure $progressCallback = null) {
 		$systemAddressBook = $this->getLocalSystemAddressBook();
 		$this->userManager->callForAllUsers(function ($user) use ($progressCallback) {
 			$this->updateUser($user);

apps/dav/lib/Connector/Sabre/Directory.php

@@ -84,7 +84,7 @@ class Directory extends Node implements ICollection, IQuota, IMoveTarget {
 	 * @param ObjectTree|null $tree
 	 * @param \OCP\Share\IManager $shareManager
 	 */
-	public function __construct($view, $info, ObjectTree $tree = null, $shareManager = null) {
+	public function __construct($view, $info, ?ObjectTree $tree = null, $shareManager = null) {
 		parent::__construct($view, $info, $shareManager);
 		$this->tree = $tree;
 	}

apps/dav/lib/Connector/Sabre/Exception/FileLocked.php

@@ -28,7 +28,7 @@
 use Exception;
 
 class FileLocked extends \Sabre\DAV\Exception {
-	public function __construct($message = '', $code = 0, Exception $previous = null) {
+	public function __construct($message = '', $code = 0, ?Exception $previous = null) {
 		if ($previous instanceof \OCP\Files\LockNotAcquiredException) {
 			$message = \sprintf('Target file %s is locked by another process.', $previous->path);
 		}

apps/dav/lib/Connector/Sabre/Exception/FileNameTooLong.php

@@ -25,7 +25,7 @@
 use Exception;
 
 class FileNameTooLong extends \Sabre\DAV\Exception {
-	public function __construct($message = '', $code = 0, Exception $previous = null) {
+	public function __construct($message = '', $code = 0, ?Exception $previous = null) {
 		if ($message === '') {
 			$message = 'File name is too long.';
 		}

apps/dav/lib/Connector/Sabre/Exception/Forbidden.php

@@ -34,7 +34,7 @@ class Forbidden extends \Sabre\DAV\Exception\Forbidden {
 	 * @param bool $retry
 	 * @param \Exception $previous
 	 */
-	public function __construct($message, $retry = false, \Exception $previous = null) {
+	public function __construct($message, $retry = false, ?\Exception $previous = null) {
 		parent::__construct($message, 0, $previous);
 		$this->retry = $retry;
 	}

apps/dav/lib/Connector/Sabre/File.php

@@ -75,7 +75,7 @@ class File extends Node implements IFile, IFileNode {
 	 * @param \OCP\Files\FileInfo $info
 	 * @param \OCP\Share\IManager $shareManager
 	 */
-	public function __construct($view, $info, $shareManager = null, Request $request = null) {
+	public function __construct($view, $info, $shareManager = null, ?Request $request = null) {
 		if (isset($request)) {
 			$this->request = $request;
 		} else {

apps/dav/lib/Connector/Sabre/FilesPlugin.php

@@ -466,7 +466,7 @@ public function handleUpdateProperties($path, PropPatch $propPatch) {
 	 * @param \Sabre\DAV\INode $node
 	 * @throws \Sabre\DAV\Exception\BadRequest
 	 */
-	public function sendFileIdHeader($filePath, \Sabre\DAV\INode $node = null) {
+	public function sendFileIdHeader($filePath, ?\Sabre\DAV\INode $node = null) {
 		// chunked upload handling
 		if (\OC_FileChunking::isWebdavChunk()) {
 			list($path, $name) = \Sabre\Uri\split($filePath);

apps/dav/lib/Connector/Sabre/MaintenancePlugin.php

@@ -43,7 +43,7 @@ class MaintenancePlugin extends ServerPlugin {
 	/**
 	 * @param IConfig $config
 	 */
-	public function __construct(IConfig $config = null) {
+	public function __construct(?IConfig $config = null) {
 		$this->config = $config;
 		if ($config === null) {
 			$this->config = \OC::$server->getConfig();