N/A service banner and notifying user about unsupported service

```
[!] Nmap reports 10.35.100.202:49258 is running: []. There are no commands to run against  in config.ini.
```
appears when a service name cannot be identified, such as

![grafik](https://user-images.githubusercontent.com/6714156/78031907-7a0fc880-7364-11ea-8004-4d0b75eb7961.png)

suggestion: a more user-friendly message in the empty brackets?