Conditional variable field data for email submission

I'm wondering if it's possible to set up a conditional variable for a send email CC. I have a text field set to populate the CC field. But I need for that field to be nullable. Currently, the form will not submit unless that text field contains an email address. 

Any thoughts on how to make this conditional? Thanks. 

[Moved from Community Help (which is about the forums) to a better forum... Mod]