Fatal error when emailing form Custom Search - csid empty

http://forum.civicrm.org/index.php/topic,12629.0.html

This can be reproduced on de demo:

Search >> Custom Searches >> Search by date added.
Select one or more contacts from result
Select "Send email to contacts"
Compose an email
Send the mail.

Fatal error will be produced.
As described on the forum-topic csid is empty in CRM_Contact_Form_Search_Custom when performing postProcess.
On the demo "Woody Woodpacker" has a valid mail for test.
(Filter on search dates: from march 08 to march 09)

// This function was OK in version 3.0.4.