Generated config has "undefined" as remote

Related to #22 (closed)

Issue description

When I write a hostname into the server address field (which is not allowed currently, see linked issue) and then click "Download" button, generated config file has following line:

remote undefined 1194

Which makes the client configuration unusable.

Proposed fix

When a user writes non-valid value into the address/host field, "Download" button should not be clickable. Alternatively, the config file should include original WAN address, but I find the former variant more correct and intuitive for a user.