use the existing vanity url in the vanity address mapping

Author: kar2905

Vanity.sol

@@ -168,9 +168,9 @@ contract VanityURL is Ownable {
   function to change vanity URL owner
   */
   function transferOwnershipForVanityURL(address _to) public {
-    require(bytes(address_vanity_mapping[_to]).length == 0);
+    require(bytes(address_vanity_mapping[_to]).length != 0);
     address_vanity_mapping[_to] = address_vanity_mapping[msg.sender];
-    vanity_address_mapping[_vanity_url] = _to;
+    vanity_address_mapping[address_vanity_mapping[msg.sender]] = _to;
     delete(address_vanity_mapping[msg.sender]);
   }