handle new UPnP return value

[tersec]

• fix/update UPNP_GetValidIGD() return value handling nim-nat-traversal#29

[tersec]

devel build errors are due to nim-lang/Nim#24090

[NimScript] exec: nim c  --styleCheck:usages --styleCheck:error --verbosity:0 --hints:off --skipUserCfg --nimcache:build/nimcache -f --warning[ObservableStores]:off -d:nimOldCaseObjects -d:chronicles_log_level=TRACE --threads:on -d:release  --mm:refc -r --outdir:build/p2p tests/p2p/all_tests
/home/runner/work/nim-eth/nim-eth/tests/p2p/test_enr.nim(22, 1) template/generic instantiation of `suite` from here
/home/runner/work/nim-eth/nim-eth/tests/p2p/test_enr.nim(51, 3) template/generic instantiation of `test` from here
/home/runner/.nimble/pkgs2/unittest2-0.2.2-6ac7f7ea74df812a25be5d6d36a59d23789eb508/unittest2.nim(1127, 24) template/generic instantiation of `failingOnExceptions` from here
/home/runner/.nimble/pkgs2/unittest2-0.2.2-6ac7f7ea74df812a25be5d6d36a59d23789eb508/unittest2.nim(1131, 26) template/generic instantiation of `failingOnExceptions` from here
/home/runner/work/nim-eth/nim-eth/tests/p2p/test_enr.nim(55, 19) Error: cannot instantiate: 'Opt[T]'; Maybe generic arguments are missing?