Error when hovering over buffer source in completion list

[Euro20179]

Make sure you have done the following

• I have updated to the latest version of blink.cmp
• I have read the README

Bug Description

When hovering over a buffer item in the completion list, an error is shown /lua/blink/cmp/windows/documentation.lua:53: attempt to index local 'item' (a nil value)

I fixed this by simply adding item == nil or to the start of the if statement on line 53.

I'm not sure why item is nil in the first place though.

Relevant configuration

sources = {
    completion = {
        enabled_providers = { "lsp", "path", "snippets", "buffer" }
    },
}

### neovim version

NVIM v0.11.0-dev-1065+gff93cccbc1

### `blink.cmp` version: branch, tag, or commit

HEAD (a62b555)