Empty address field set in submitted profile overwrites existing address data when updating an existing (matched) contact

(Lobo - Expected behavior is that if all address fields are empty, we don't overwrite existing address data. Assigning to you to further determine if this is a bug / and what the right fix is).

Steps to recreate:

• existing contact with Home Address fields populated and a 'known' email address'
• associate sample Name and Address profile w/ the sample Fall Fundraiser event
• register for Fall Fundraiser as anonymous user, and enter matching email address for contact above
• leave all address fields in the profile blank

When you look at the contact record after registration, the home address fields are empty. This occurs regardless of whether you leave the 'default' country (United States) selected in the profile form OR change it to null choice ('select').