fix creating users

lib/user.php

@@ -166,8 +166,10 @@ class OC_USER {
 		if( $run ){
 			//delete the user from all backends
 			foreach(self::$_usedBackends as $backend){
+				if($backend->implementsActions(OC_USER_BACKEND_DELETE_USER)){
 					$backend->deleteUser($uid);
 				}
+			}
 			// We have to delete the user from all groups
 			foreach( OC_GROUP::getUserGroups( $uid ) as $i ){
 				OC_GROUP::removeFromGroup( $uid, $i );
@@ -270,10 +272,12 @@ class OC_USER {
 
 		if( $run ){
 			foreach(self::$_usedBackends as $backend){
+				if($backend->implementsActions(OC_USER_BACKEND_SET_PASSWORD)){
 					if($backend->userExists($uid)){
 						$backend->setPassword($uid,$password);
 					}
 				}
+			}
 			OC_HOOK::emit( "OC_USER", "post_setPassword", array( "uid" => $uid, "password" => $password ));
 			return true;
 		}
@@ -292,12 +296,14 @@ class OC_USER {
 	 */
 	public static function checkPassword( $uid, $password ){
 		foreach(self::$_usedBackends as $backend){
+			if($backend->implementsActions(OC_USER_BACKEND_CHECK_PASSWORD)){
 				$result=$backend->checkPassword( $uid, $password );
 				if($result===true){
 					return true;
 				}
 			}
 		}
+	}
 
 	/**
 	 * @brief Get a list of all users
@@ -322,11 +328,13 @@ class OC_USER {
 	 */
 	public static function userExists($uid){
 		foreach(self::$_usedBackends as $backend){
+			if($backend->implementsActions(OC_USER_BACKEND_USER_EXISTS)){
 				$result=$backend->userExists($uid);
 				if($result===true){
 					return true;
 				}
 			}
+		}
 		return false;
 	}
 }