Fix undefined local network address

[wabscale]

In the event that serve is started when the host machine is not connected to the internet, the local network address will show up as undefined. Adding a simple check fixes this. When this is the case, the local network address won't appear anymore.

• Fix undefined local network address

[leerob]

null is not an improvement over undefined here, so I'm going to close this as won't fix. Thank you regardless 🙏

[wabscale]

If you read a few lines down, if networkAddress is null then it does not print it out. It does not print null.

https://github.com/vercel/serve/blob/master/bin/serve.js#L245

[wabscale]

Here is how it looks right now in the master branch:

And here is what it looks like after my change:

[leerob]

My apologies - I definitely read this wrong!

[leerob]

Thank you!