fix(log): Handle case when error code is missing

[sorin-davidoi]

To reproduce supply a custom certificate with altnames (e.g. localhost:5000) that does not include localhost:<port> and start server on localhost:<port> (e.g. localhost:3000).

Before

[HPM] Error occurred while trying to proxy request <redacted> from <redacted> to <redacted> (undefined) (https://nodejs.org/api/errors.html#errors_common_system_errors)

After

[HPM] Error occurred while trying to proxy request <redacted> from <redacted> to <redacted> (Error: Hostname/IP doesn't match certificate's altnames: "Host: <redacted>. is not in the cert's altnames: DNS:<redacted>, DNS:<redacted>") (https://nodejs.org/api/errors.html#errors_common_system_errors)

[coveralls]

Coverage remained the same at 97.067% when pulling 4a4e112 on sorin-davidoi:patch-1 into 029c99d on chimurai:master.

[chimurai]

Thanks @sorin-davidoi .

Can you update the PR description on how to reproduce this issue?

[brettdh]

See also #263 for a variant (err.reason). I have no strong opinion about which is better, but it would be great to get one of these merged.

I haven't tested a minimal example, but I suspect that another way to reproduce this would be to copy the basic https recipe and remove "changeOrigin": true (adding it to my config resolved the similar altnames error I was seeing).