bug: config.opts treats empty table as nil

[mvllow]

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• I have searched the exsiting issues of plugins related to this issue

Neovim version (nvim -v)

NVIM v0.9.0-dev-1834+gf7ad46e69-dirty

Operating system/version

macOS Ventura 13.2

Describe the bug

Setting opts to an empty table results in nil. Some plugins require an empty table to use the default config, e.g. mason-tool-installer.nvim

Failed to run `config` for mason-tool-installer.nvim                           
vim/shared.lua:0: after the second argument: expected table, got nil

Currently, you must do opts = { key = "value" } or similar for the table to be recognised.

Steps To Reproduce

1. Use the repro below
2. Let lazy install necessary plugins, using opts = {} for mason-tool-installer.nvim
3. Reopen Neovim to be greeted with the "expected table, got nil" error

Expected Behavior

Passing opts = {} should result in plugin.setup({}).

Repro

-- DO NOT change the paths and don't remove the colorscheme
local root = vim.fn.fnamemodify("./.repro", ":p")

-- set stdpaths to use .repro
for _, name in ipairs({ "config", "data", "state", "cache" }) do
	vim.env[("XDG_%s_HOME"):format(name:upper())] = root .. "/" .. name
end

-- bootstrap lazy
local lazypath = root .. "/plugins/lazy.nvim"
if not vim.loop.fs_stat(lazypath) then
	vim.fn.system({ "git", "clone", "--filter=blob:none", "https://github.com/folke/lazy.nvim.git", lazypath })
end
vim.opt.runtimepath:prepend(lazypath)

-- install plugins
local plugins = {
	"folke/tokyonight.nvim",
	{
		"WhoIsSethDaniel/mason-tool-installer.nvim",
		dependencies = { "williamboman/mason.nvim", config = true },
		opts = {},
	},
}
require("lazy").setup(plugins, {
	root = root .. "/plugins",
})

vim.cmd.colorscheme("tokyonight")
-- add anything else here

[folke]

I'd argue that this should be fixed in mason-tools-installer, but I've changed it anyway since it probably makes more sense to let it always be a table.

There are other plugins that will break now though, but for those they just need to use a config() function instead. like #208

[mvllow]

That makes sense, so config = true would be for nil opts. I agree that it would be nice for plugins to not expect an empty table.

Appreciate the fix :)