"list index out of range" when no command is defined

[Sainan]

Describe the bug
"command" is documented as "can be empty if starting manually, then TCP transport must be configured". However, doing so raises "list index out of range". This is possibly a regression of #1564.

To Reproduce
Use the following user configuration:

{
    "clients": {
        "pluto-language-server": {
            "enabled": true,
            "selector": "source.lua",
            "tcp_port": 5007,
            "command": []
        }
    }
}

Expected behavior
It shouldn't've attempted to start the process with the [] configuration.

Screenshots

Environment:

• OS: Windows 10
• Sublime Text version: 4143
• LSP version: 1.20.0
• Language servers used: pluto-language-server

[predragnikolic]

The "list index out of range" error should be fixed with #2300

Feel free to reopen, if you stumble upon any issue.