fix: support calling setup() w/o args

[tmfink]

Avoids error attempt to index local 'opts' (a nil value) when calling setup() without arguments.

I noticed the issue when I updated the plugin.

Snippet of my init.lua, which does not pass arguments to setup():

-- install w/ vim-plug
vim.call('plug#begin')
Plug('tris203/precognition.nvim')
vim.call('plug#end')

... 

require('precognition').setup()

[tris203]

Good catch @tmfink

This would have been since the introduction of the color adjustment stuff.

In lazy it would give you a type warning, but Im guessing Packer doesn't do that

[tris203]

Thanks

Will merge this in the next few days

[tris203]

Thanks!