fix(files): Ensure that the hash method does not return null

To match https://github.com/nextcloud/server/blob/beececf66068f57c416225efcde9b44ce5c2e835/lib/private/Files/View.php#L1050

- Fix #44110

Signed-off-by: Louis Chemineau <louis@chmn.me>

lib/private/Files/Storage/Local.php

@@ -399,8 +399,15 @@ public function fopen($path, $mode) {
 		return $result;
 	}
 
-	public function hash($type, $path, $raw = false) {
-		return hash_file($type, $this->getSourcePath($path), $raw);
+	public function hash($type, $path, $raw = false): string|false {
+		/** @var string|false|null */
+		$hash = hash_file($type, $this->getSourcePath($path), $raw);
+
+		if ($hash === null) {
+			return false;
+		}
+
+		return $hash;
 	}
 
 	public function free_space($path) {

lib/private/Files/Storage/Wrapper/Availability.php

@@ -315,6 +315,7 @@ public function hash($type, $path, $raw = false) {
 			return parent::hash($type, $path, $raw);
 		} catch (StorageNotAvailableException $e) {
 			$this->setUnavailable($e);
+			return false;
 		}
 	}