src: connection: Fix panic when DNS lookup fails #416

Job	Run time
quick-tests	1m 13s
build (macos-latest, x86_64-apple-darwin, --features all-dialects)	3m 48s
build (ubuntu-latest, arm-unknown-linux-musleabihf, --features ardupilotmega)	1m 48s
build (ubuntu-latest, armv7-unknown-linux-musleabihf, --features ardupilotmega)	1m 40s
build (ubuntu-latest, x86_64-unknown-linux-musl, --features all-dialects)	2m 4s
build (ubuntu-latest, x86_64-unknown-linux-musl, --features all-dialects,emit-extensions)	1m 59s
build (ubuntu-latest, thumbv7m-none-eabi, --no-default-features --features embedded)	1m 11s
build (windows-latest, x86_64-pc-windows-msvc, --features all-dialects)	2m 39s
test-embedded-size	35s
	16m 57s

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