as found by @mhils and me in mitmproxy/mitmproxy#4451 (comment) ff,
pyopenssl does not check the return code of SSL_CTX_set_alpn_protos(),
https://github.com/pyca/pyopenssl/blob/d182dab3f7b51c3f3d5c13687f1abba81acd78e4/src/OpenSSL/SSL.py#L137882
while that function fails on input as simple as an empty list.