fix(udp/fast-apple): ignore empty cmsghdr #5439

Job	Run time
test on illumos	8m 16s
test on netbsd	6m 7s
test on freebsd	5m 34s
test (ubuntu-latest, stable)	1m 7s
test on solaris	5m 36s
test (ubuntu-latest, beta)	1m 2s
audit	25s
test (macos-latest, stable)	1m 11s
features (ubuntu-latest)	1h 59m 0s
test (windows-latest, stable)	4m 11s
features (macos-latest)	38m 54s
lint	1m 40s
features (windows-latest)	1h 6m 30s
msrv	18s
test-android (x86_64-linux-android, x86_64, 26)	3m 6s
test-aws-lc-rs	59s
test wasm32-unknown-unknown	1m 23s
test-android (x86_64-linux-android, x86_64, 25)	2m 45s
test-android (i686-linux-android, x86, 26)	2m 24s
test-android (i686-linux-android, x86, 25)	2m 28s
	4h 32m 56s

Provide feedback