fix: fix getting groupfolder mount for users home directory

Signed-off-by: Robin Appelman <robin@icewind.nl>

Author: icewind1991

lib/Mount/MountProvider.php

@@ -284,7 +284,11 @@ public function getMountsForPath(string $setupPathHint, bool $forChildren, array
 				continue;
 			}
 
-			$userFolders[$user->getUID()] ??= $this->folderManager->getFoldersForUser($user, null, implode('/', array_splice($parts, 3, -1)), $forChildren);
+			$relativePath = implode('/', array_splice($parts, 3, -1));
+			if ($relativePath === '') {
+				$relativePath = '/';
+			}
+			$userFolders[$user->getUID()] ??= $this->folderManager->getFoldersForUser($user, null, $relativePath, $forChildren);
 			$folders = $userFolders[$user->getUID()];
 
 			foreach ($folders as $folder) {