Ignore user null check

[panbohaha]

when deploy to docker, we can't get the Username or User from evn.

[hakenmt]

Could probably just set USER or USERNAME in the docker environment? There are other places that check for the username to not be null or empty, particularly here

PrestoClient/PrestoClient/PrestodbClient.cs

Line 1025 in 7210e48

private bool CheckConfiguration(out Exception ex)

, which is called before executing query. So allowing a username to be null or empty has some cascading effects. Is there a better default value for this when run in a docker environment?

[panbohaha]

yes, for now, we add the UserName into docker env. I think the CheckConfiguration function is okay. for my issue is when init the class PrestoClientSessionConfig we got the error.
the code is like this:

var config = new PrestoClientSessionConfig(){
UserName = "test"
};