bug fix: candidate email encryption on empty email

app/services/crypt_serializer.rb

@@ -26,7 +26,7 @@ class CryptSerializer
       raise "Attribute was supposed to be a `String`, but was instead a `#{value.class}`"
     end
 
-    return value if value.nil?
+    return nil if value.blank?
 
     cipher.encrypt
     parts = [cipher.random_key, cipher.random_iv, cipher.update(value) + cipher.final]