Preview fails on all UNC paths: ArgumentException "Illegal characters in path" (mapped drive works)

[18734860425yt-a11y]

Environment: QuickLook 4.5.0 (GitHub release), Windows 10.0.19041.2

Steps to reproduce:

1. Open any folder on an SMB network share in File Explorer, e.g. \server\share\folder
2. Select an image file (e.g. .png) and press Spacebar
3. QuickLook shows the fallback info card (path/size/date) instead of the image preview
4. Pressing Spacebar again may show an error dialog: System.ArgumentException: Illegal characters in path

Stack trace (from the error dialog, ResolveShortcut → Path.CheckInvalidPathChars):

System.ArgumentException: 路径中具有非法字符。
在 System.IO.Path.CheckInvalidPathChars(String path, Boolean checkAdditional)
在 System.IO.Path.GetExtension(String path)
在 QuickLook.Plugin.QuickLook.Plugin.ResolveShortcut(String path)
在 QuickLook.ViewWindowManager.TogglePreview(String path, Boolean isFromPipe)

Findings:

• Fails with all UNC forms: \server.domain\share, \shortname\share, and \10.x.x.x\share
• The exact same files preview correctly when the share is accessed via a mapped drive letter (Z:...)
• Local files preview correctly
• Possibly related to Error when previewing image/video/HTML files in WSL #617 (UriFormatException on \wsl$... — also UNC-path parsing, different exception)

Expected: files on UNC paths should preview like local ones; at minimum, ArgumentException should be caught in ResolveShortcut.