API: Fix PHP error when given a list of uids to delete. Bug #12790

When we pass an array of uids to delete,
we should return after processing them.

Fixes this error when using a Kolab backend:
2013-10-23T10:53:27+02:00 WARN: HORDE [mnemo] PHP ERROR: base64_encode() expects parameter 1 to be string, array given [pid 11460 on line 375 of "/datastore/share/pear/Horde/Url.php"]

Signed-off-by: Michael J Rubinsky <mrubinsk@horde.org>