Fix behavior of default email/phone field with empty value

tailbone/forms/fields.py

@@ -72,9 +72,12 @@ class DefaultEmailField(fa.Field):
             address = self._deserialize()
             contact = self.parent.model
             if contact.emails:
+                if address:
                     email = contact.emails[0]
                     email.address = address
                 else:
+                    contact.emails.pop(0)
+            elif address:
                 email = contact.add_email_address(address)
 
 
@@ -96,7 +99,10 @@ class DefaultPhoneField(fa.Field):
             number = self._deserialize()
             contact = self.parent.model
             if contact.phones:
+                if number:
                     phone = contact.phones[0]
                     phone.number = number
                 else:
+                    contact.phones.pop(0)
+            elif number:
                 phone = contact.add_phone_number(number)