DNS: fix parsing of hostname for empty response messages #5199

Job	Run time
Python Bindings (ubuntu-latest)	1m 0s
ubuntu-22.04 cc	5m 5s
LTO and Gold Linker gcc-14	2m 32s
ubuntu-24.04 cc	6m 27s
LTO and Gold Linker clang-18	2m 5s
Test Utils (ubuntu-latest)	2m 53s
macOS-13 cc	4m 8s
macOS-14 cc	2m 18s
windows-latest (msys2)	7m 40s
macOS-15 cc	2m 26s
ubuntu-22.04-arm cc	3m 54s
ubuntu-24.04-arm cc	3m 41s
ubuntu-22.04 gcc-4.9 --with-pcre2 --with-maxminddb --with-sanitizer	8m 58s
ubuntu-24.04 gcc-14 --with-pcre2 --with-maxminddb --with-sanitizer	12m 36s
ubuntu-22.04 clang-12 --with-pcre2 --with-maxminddb --with-sanitizer	13m 35s
ubuntu-24.04 clang-18 --with-pcre2 --with-maxminddb --with-sanitizer	15m 38s
ubuntu-latest cc --with-pcre2 --with-maxminddb nBPF	3m 45s
ubuntu-latest cc --with-pcre2 --with-maxminddb --disable-global-context-support	5m 34s
macOS-latest cc --with-pcre2 --with-maxminddb	2m 40s
	1h 46m 55s

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