Fix exception when calling resolveTxt with invalid unicode

[michalz-zoom]

Sometimes resolveTxt throws when called with invalid unicode.

I couldn't repro on my system, neither with nodejs dns package, nor with native-dns that's used by Keybase server.

Some hints that other people have also been hitting this in the past: nodejs/node#39139

The solution is to wrap resolveTxt call in try/catch, and report like any normal error.

[heronhaye]

i didn't realize you could try/catch callback functions like this, cool!

[michalz-zoom]

you should also be able to do something like

try
   await foo defer err, res
catch err
cb err, res

but is silently broken in iced2 😢 IIRC the code after catch is not emitted at all for some reason

[michalz-zoom]

This only catches exceptions thrown in the sync part of resolveTxt though, if theres some exception in some callback afterwards, or even in the callback we supply here, it's not going to be caught by the try block.