fix: fix case where LSP progress autocommand errors because the value of the status is nil

Some language servers seem to improperly implement the lsp progress
operations. This isn't technically our problem, but we can protect
against this edge case easily without much work.

Closes #38

Author: mehalter

lua/astrolsp/init.lua

@@ -54,7 +54,7 @@ function M.progress(data)
   local id = ("%s.%s"):format(data.client_id, data.params.token)
   M.lsp_progress[id] = M.lsp_progress[id] and vim.tbl_deep_extend("force", M.lsp_progress[id], data.params.value)
     or data.params.value
-  if M.lsp_progress[id].kind == "end" then
+  if not M.lsp_progress[id] or M.lsp_progress[id].kind == "end" then
     vim.defer_fn(function()
       M.lsp_progress[id] = nil
       lsp_event "Progress"