opt.get_option in on_attach() returns nil for unset options #402

When I try to active completion-nvim in my init.lua with the on_attach function, I get a bunch of errors.

Error running config for completion-nvim: ...ite/pack/packer/start/completion-nvim/lua/completion.lua:251: bad argument #1 to 'ipairs' (table expected, got nil)

If we look at the offending line:

disable_filetypes which is returned by get_options is nil the moment ipairs is called. I tried to manually edit the file and add disable_filetypes = disable_filetypes or {} at line 250 but I got basically the same error elsewhere.

Error running config for completion-nvim: ...ite/pack/packer/start/completion-nvim/lua/completion.lua:266: bad argument #1 to 'len' (string expected, got nil)

which is basically the same error.

string.len() is getting nil as its argument.

My testing minimal init.lua

require('completion').on_attach()

(literally my one-line init.lua created in a temporary home directory)

Expected behavior
I expect not to get errors when I call on_attach. Perhaps get_options should handle missing options better (?)