bug v3: Preview goes on inifinite error loop if buffer is deleted while symbols / definitions are open.

[arieldd]

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Neovim version (nvim -v)

v0.10.0-dev-3116+gc1396afa7

Operating system/version

WSL - Ubuntu 22

Describe the bug

When closing a buffer via buffer delete (:bd) when either LSP symbols or definitions window is open, Preview keeps trying to index a null value and goes on an infinite error loop.

Steps To Reproduce

1- Open any file with LSP symbols support
2- Toggle LSP Symbols window
3- Close buffer with :bd
4- If it does not trigger on first try, navigate to one of the symbols and try again.

Expected Behavior

Either symbols / definitions windows close with the buffer or they stay open without errors.

[arieldd]

This can also be triggered when attempting to open Symbols window when no buffer is open, e.g. from an Alpha Dashboard.