bug: indexing a nil when highlight.pattern = ""

[h3xOo]

Did you check docs and existing issues?

• I have read all the todo-comments.nvim docs
• I have updated the plugin to the latest version before submitting this issue
• I have searched the existing issues of todo-comments.nvim
• I have searched the existing issues of plugins related to this issue

Neovim version (nvim -v)

NVIM v0.10.3 Build type: RelWithDebInfo LuaJIT 2.1.1731601260

Operating system/version

Artix Linux 6.12.8

Describe the bug

When I set a highlight.pattern to "" or " ", then running TodoTelescope or TodoTroubles tries to index a nil, in lua/telescope/_extensions/todo-comments.lua:44 or lua/trouble/sources/todo.lua:14.

Steps To Reproduce

1. Set highlight.pattern to empty string
2. Run TodoTelescope

Expected Behavior

It wouldn't fail.

Repro

vim.env.LAZY_STDPATH = ".repro"
load(vim.fn.system("curl -s https://raw.githubusercontent.com/folke/lazy.nvim/main/bootstrap.lua"))()

require("lazy.minit").repro({
        spec = {
                {
                        "folke/todo-comments.nvim",
                        lazy = false,
                        opts = {
                                highlight = {
                                        pattern = "",
                                },
                        }
                },
                {
                        "nvim-telescope/telescope.nvim",
                        lazy = false,
                        version = false,
                },
        },
})

[tgallacher]

Also hitting this issue after changing the default search/highlight patterns based on #255