Currently I'm working with windows credentials, when i trying to create a user with SQL Authentication encountered the attached error. I have seen it is due to empty login name. How to resolve this issue.
Are you trying to create empty login?
CREATE LOGIN  FROM WINDOWS WITH DEFAULT_DATABASE=[master]
If we run above in the SSMS query window, we get below error message:
Msg 1038, Level 15, State 4, Line 1 An object or column name is missing or empty. For SELECT INTO statements, verify each column has a name. For other statements, look for empty alias names. Aliases defined as “” or  are not allowed. Change the alias to a valid name.
Now the error makes sense;
Because login is created as  and error clearly says that “… are not allowed…”
The issue was caused because of the empty login name. If we provide name, then the issue will be resolved.
For more info check CREATE LOGIN