When client script is used to make a field not mandatory, the field is instead made mandatory.

1. Create a client script to make the Short Description field of a change request NOT mandatory.
   An example client script is attached to this article.
2. Open a change request record.
   Note that the Short Description field does not appear to be mandatory.
3. Clear the Short Description field and try to save the record.
   A warning is displayed stating that the short description is mandatory and the record cannot be saved. 

Work around the issue by setting your script to use a boolean argument rather than a string:

Before: g_form.setMandatory(field, 'false')

After: g_form.setMandatory(field, false);