Add changelog message

Author: gumb0

CHANGELOG.md

@@ -10,5 +10,6 @@
 - Fixed: [#5512](https://github.com/ethereum/aleth/pull/5512) Calling `eth_call` without `from` argument. 
 - Fixed: [#5502](https://github.com/ethereum/aleth/pull/5502) Fix Discovery terminating prematurely because of race condition.
 - Fixed: [#5452](https://github.com/ethereum/aleth/pull/5452) Correctly handle Discovery messages when the peer changes public key.
+- Fixed: [#5519](https://github.com/ethereum/aleth/pull/5519) Correctly handle Discovery messages with known public key but unknown endpoint.
 
 [1.6.0]: https://github.com/ethereum/aleth/compare/v1.6.0-alpha.1...master