Fix windows DNS crash on bootup

[adfoster-r7]

Closes #19516

Best reviewed with whitespace ignored

Verification

I manually set arr to match the user's resolv info of a nil searchlist.

Before

Crash

c:/a/metasploit-framework/lib/net/dns/resolver.rb:282:in `searchlist=': Wrong argument format, neither String nor Array (ResolverArgumentError)
        from c:/a/metasploit-framework/lib/net/dns/resolver.rb:1086:in `parse_config_file'
        from c:/a/metasploit-framework/lib/rex/proto/dns/resolver.rb:66:in `initialize'
        from c:/a/metasploit-framework/lib/rex/proto/dns/cached_resolver.rb:25:in `initialize'
        from c:/a/metasploit-framework/lib/msf/ui/console/driver.rb:86:in `new'
        from c:/a/metasploit-framework/lib/msf/ui/console/driver.rb:86:in `initialize'
        from c:/a/metasploit-framework/lib/metasploit/framework/command/console.rb:66:in `new'
        from c:/a/metasploit-framework/lib/metasploit/framework/command/console.rb:66:in `driver'
        from c:/a/metasploit-framework/lib/metasploit/framework/command/console.rb:54:in `start'
        from c:/a/metasploit-framework/lib/metasploit/framework/command/base.rb:82:in `start'
        from msfconsole:23:in `<main>'

After

verified there was no longer a crash:

msf6 >

[adfoster-r7]

Not a blocker for me; but looks like there's an existing edge-case here, where we might be have partially parsed this file before encountering an error - and we don't revert state back, or continue parsing the rest of the file