fix(lsp): avoid accessing undefined user_data (#2216)

Co-authored-by: Alexey Svirshchevskiy <alexey.svirshchevskiy@sitoo.com>

lua/lvim/lsp/config.lua

@@ -23,7 +23,7 @@ return {
       prefix = "",
       format = function(d)
         local t = vim.deepcopy(d)
-        local code = d.code or d.user_data.lsp.code
+        local code = d.code or (d.user_data and d.user_data.lsp.code)
         if code then
           t.message = string.format("%s [%s]", t.message, code):gsub("1. ", "")
         end