fix(lsp): do a nil check before string matching autocmd desc (#3354)

lua/lvim/lsp/manager.lua

@@ -62,7 +62,7 @@ local function client_is_configured(server_name, ft)
   ft = ft or vim.bo.filetype
   local active_autocmds = vim.api.nvim_get_autocmds { event = "FileType", pattern = ft }
   for _, result in ipairs(active_autocmds) do
-    if result.desc:match("server " .. server_name .. " ") then
+    if result.desc ~= nil and result.desc:match("server " .. server_name .. " ") then
       Log:debug(string.format("[%q] is already configured", server_name))
       return true
     end