New XUL: "Edit due date" crashes out with "Invalid date format"

* Evergreen rel_2_3 as of 2.3.0-beta1

Method to reproduce:

1. Check out an item to a patron
2. In "Items Out" tab, select the item, right-click, and choose "Edit due date"
3. Change the date to, say, "2012-08-07"*

* Note that our system is configured with the actor.org_unit_setting format.date = "yyyy-MM-dd"

Expected results:

The due date will be changed to 2012-08-07.

Actual result:

The attempt fails, with the following error displayed to the staff user:

method=open-ils.circ.circulation.due_date.update
params=["cad9ddbc255980c4c662fe7dd356e950",726231,null]
THROWN:
{"payload":[],"debug":"osrfMethodException : *** Call to [open-ils.circ.circulation.due_date.update] failed for session [1344360665.461238.134436066519449], thread trace [1]:\nInvalid date format: at /usr/share/perl5/Error.pm line 416.\n\n","status":500}
STATUS: