Pressing 'Enter' while entering custom field bypasses required field check

What steps will reproduce the problem?
1. Choose "Create Inventory" in the Inventory tab
2. Type something into a custom field and hit the Enter key on the keyboard
3. An item is created without required fields, which prevents the inventory 
section from working.

What is the expected output? What do you see instead?

Fatal error: Call to a member function __toString() on a non-object in 
/home/jabber/www/tracmor-0.3.0/includes/qcodo/_core/qform/QDataGridBase.class.ph
p(359) : eval()'d code on line 1

What version of the product are you using? On what operating system?
tracmor-0.3.0 on Debian 5.0

Please provide any additional information below.

Here is the item in the mysql database:

mysql> SELECT * FROM inventory_model WHERE inventory_model_id=8;
+--------------------+-------------+-----------------+----------------------+---
----------------+------------------+------------+-------+------------+----------
-----------+-------------+---------------+
| inventory_model_id | category_id | manufacturer_id | inventory_model_code | 
short_description | long_description | image_path | price | created_by | 
creation_date       | modified_by | modified_date |
+--------------------+-------------+-----------------+----------------------+---
----------------+------------------+------------+-------+------------+----------
-----------+-------------+---------------+
|                  8 |        NULL |            NULL |                      |   
                |                  | NULL       |  NULL |          1 | 
2010-12-14 11:25:06 |        NULL |          NULL |
+--------------------+-------------+-----------------+----------------------+---
----------------+------------------+------------+-------+------------+----------
-----------+-------------+---------------+
1 row in set (0.00 sec)

If I remove this item, the problem goes away until the next time someone hits 
'Enter' in a custom field when creating an inventory item.

Original issue reported on code.google.com by tor...@gmail.com on 14 Dec 2010 at 7:29

sukhvir007 / tracmor

Pressing 'Enter' while entering custom field bypasses required field check #83