Diagnostics in untitled files in Visual Studio Code aren't being targeted to the untitled file

[ShamblesSM]

How are you using the lua-language-server?

Visual Studio Code Extension (sumneko.lua)

Which OS are you using?

Windows

What is the issue affecting?

Diagnostics/Syntax Checking

Expected Behaviour

Untitled files should be given diagnostics just like saved files.

Actual Behaviour

Untitled files aren't getting the diagnostics. While the diagnostics themselves work, the "file" that the diagnostics are reporting point to a non-existent file.

Reproduction steps

1. Create a new file.
2. Type anything that would cause diagnostics to kick in (such as a syntax error).
3. Notice the lack of squiggly lines.

Additional Notes

Log File

service.log