ComboBox getValue occurs a null exception

[GoogleCodeExporter]

What steps will reproduce the problem?
1.through the Record's getAsString if the value is null
2.then set the value to ComboBox 
3.last getValue by the ComboBox will reproduce the null exception

What is the expected output? What do you see instead?
expected get the null value not reproduce a null exception;
instead,we can modify the ComboBox's getValue method's code,like this:
(val === undefined || val == null || val === '') ? null : val.toString();
before it didn't judge the val == null condition

Please use labels and text to provide additional information.
Record.getAsString:if value === undefined || value == null || value === '' will 
return null;
combobox getValue: val === '' ? null : val.toString();

Original issue reported on code.google.com by yzs1...@gmail.com on 30 Nov 2011 at 2:27