dont try to use the filesystem when it isnt setup yet

apps/files_sharing/sharedstorage.php

@@ -22,7 +22,7 @@
 
 require_once( 'lib_share.php' );
 
-if (!OC_Filesystem::is_dir('/Shared')) {
+if (OC_Filesystem::$loaded and !OC_Filesystem::is_dir('/Shared')) {
 	OC_Filesystem::mkdir('/Shared');
 }
 OC_Filesystem::mount('OC_Filestorage_Shared',array('datadir'=>'/'.OC_User::getUser().'/files/Shared'),'/'.OC_User::getUser().'/files/Shared/');

lib/filesystem.php

@@ -47,6 +47,7 @@ class OC_Filesystem{
 	static private $storages=array();
 	static private $mounts=array();
 	static private $storageTypes=array();
+	public static $loaded=false;
 	private $fakeRoot='';
 	static private $defaultInstance;
 
@@ -200,6 +201,7 @@ class OC_Filesystem{
 			return false;
 		}
 		self::$defaultInstance=new OC_FilesystemView($root);
+		self::$loaded=true;
 	}
 	
 	/**