Multiple CUG configuration - using Gigya RaaS - are there placeholder values in AEM for checking blank value fields?

Hi Community, 

I was just about to set up a multiple CUG for a few sites in AEM. As for your reference, we are using Gigya RaaS to provide login etc. Setting up CUG`s we are checking Gigya values (as for example profession) to be true to provide login to specific groups. Due to older Registration issues some accounts do have blank values (eg. in profession field) but they would require to be part of the CUG aswell. Is there a placeholder I could insert in AEM as value that accepts blank fields from Gigya? 

Thanks a lot in advance!