Error "Request textDocument/documentSymbol failed." when creating new group in locale file

[Bilka2]

When I type [ to create a new group in a locale file in a tutorial scenario, the extension errors with Request textDocument/documentSymbol failed.

Output:

[Error - 11:55:59 AM] Request textDocument/documentSymbol failed.
Error: name must not be falsy
	at r.validate (c:\Users\Erik\AppData\Local\Programs\Microsoft VS Code\resources\app\out\vs\workbench\api\node\extensionHostProcess.js:151:17855)
	at new r (c:\Users\Erik\AppData\Local\Programs\Microsoft VS Code\resources\app\out\vs\workbench\api\node\extensionHostProcess.js:151:18150)
	at Jr (c:\Users\Erik\.vscode\extensions\justarandomgeek.factoriomod-debug-1.1.42\dist\fmtk.js:168:73657)
	at s (c:\Users\Erik\.vscode\extensions\justarandomgeek.factoriomod-debug-1.1.42\dist\fmtk.js:168:48779)
	at Object.H6e [as map] (c:\Users\Erik\.vscode\extensions\justarandomgeek.factoriomod-debug-1.1.42\dist\fmtk.js:168:48865)
	at Object.zn [as asDocumentSymbols] (c:\Users\Erik\.vscode\extensions\justarandomgeek.factoriomod-debug-1.1.42\dist\fmtk.js:168:73624)
	at u (c:\Users\Erik\.vscode\extensions\justarandomgeek.factoriomod-debug-1.1.42\dist\fmtk.js:172:56093)
	at async r.provideDocumentSymbols (c:\Users\Erik\AppData\Local\Programs\Microsoft VS Code\resources\app\out\vs\workbench\api\node\extensionHostProcess.js:153:90654)

Locale file where this happens is https://github.com/Bilka2/tutorial-demo/blob/master/tutorials/demo-tut/locale/en/en.cfg. I opened the tutorial control.lua file first to make sumneko load, not sure if relevant.

VsCode 1.89.0
FMTK 1.1.42
sumneko Lua 3.7.4