Handle empty string returned from Environment.GetFolderPath

[jjonescz]

@RikkiGibson has noticed in the documentation of Environment.GetFolderPath that it might return an empty string. So this PR handles that case.

[Copilot]

Pull Request Overview

This PR adds defensive error handling for a rare edge case where Environment.GetFolderPath or Path.GetTempPath() returns an empty string, preventing potential issues downstream when attempting to construct temporary file paths for file-based app artifacts.

Key Changes

• Added a null/empty string check after obtaining the temporary directory path
• Throws an InvalidOperationException with a descriptive message if the path is empty
• Protects against potential ArgumentException or unexpected behavior when passing empty paths to Path.Join

[KalleOlaviNiemitalo]

Path.GetTempPath on Windows never returns an empty string. If GetTempPathW or GetTempPath2W returns a zero length, it throws instead. So this advice on "configuring the TEMP environment variable on Windows" will not be seen on Windows.

[MiYanni]

Might be worth having a unit test with different OSs so that we check this situation.

[jjonescz]

Path.GetTempPath on Windows never returns an empty string.

So this advice on "configuring the TEMP environment variable on Windows" will not be seen on Windows.

Having a message that is potentially never applicable seems fine to me. I don't think it is guaranteed that Path.GetTempPath will never return an empty string in the future. The purpose of this change is to defend against bad values that would cause silent bugs down the road.

Might be worth having a unit test with different OSs so that we check this situation.

I'm not sure how can I create a unit test for this. Such test would probably need to reconfigure the OS so the empty temp path is returned.