lsp_finder: not working if LSP is running in single file mode

[xeluxee]

Description

1. Open a file that's not in a project, so there is no root directory.
2. Launch :Lspsaga lsp_finder
3. A message is printed: [LspSaga] get root dir failed

Expected Behavior

Even if there's no root it should work, as trouble do (it finds references if i launch :Trouble lsp_references)

Details

Reproduce

1. Install a language server, e.g. clangd
2. Create a simple cpp file in an empty folder (not git managed, because it must run in single file mode)
3. Launch :Lspsaga lsp_finder
4. A message is printed: [LspSaga] get root dir failed

To make sure it runs in single file mode run :LspInfo and you should get an output like this (see root directory):

Environment

• nvim --version output:

NVIM v0.6.0
Build type: Release
LuaJIT 2.0.5

• Operating system: gnu/linux
• lspsaga commit: 518c12e