Failed to remove port mappings with the NAT-PMP interface

https://datatracker.ietf.org/doc/html/rfc6886#section-3.4:

"When a mapping is destroyed successfully as a result of the client
explicitly requesting the deletion, the NAT gateway MUST send a
response packet that is formatted as defined in Section 3.3,
"Requesting a Mapping". The response MUST contain a result code of
0, the internal port as indicated in the deletion request, an
external port of 0, and a lifetime of 0."

According the specs, the external port in the removal response should be zero. However, the code at https://sourceforge.net/p/dcplusplus/code/ci/default/tree/dcpp/Mapper_NATPMP.cpp#l130 makes the removal fail if the mapped public port in the response doesn't match the originally mapped one, causing an error message on every removal.