Error with calculated value in forms v 1.2.1

Hi,

 I have downloaded and installed nintex forms 1.2.1. Since this installation, I have a new issue: if a want to use a calculated value and make field 1 * field 2 I get an error when i enter a value in field 1 or field 2. The error is the following:

Error in fomula: Unable to get value of the property 'isNumeric': object is null or undefined

In previous version, the calculated value field was working correctly.

I have tried with decimal, integrer or currency. All the 3 options were generating the same error.

Please help.

Regards