fix(lsp): Handle nil message_callbacks

The `onexit` handler could set `message_callbacks` to `nil` within the
luv event loop while the mainloop runs a function that tries to access
`message_callbacks`.

This adds some checks to prevent errors in that case.

Fixes https://github.com/neovim/neovim/issues/14863

1 files changed, 3 insertions, 3 deletions

diff --git a/runtime/lua/vim/lsp/rpc.lua b/runtime/lua/vim/lsp/rpc.lua
index ea12c97d40..4c5f02af9d 100644
--- a/runtime/lua/vim/lsp/rpc.lua
+++ b/runtime/lua/vim/lsp/rpc.lua
@@ -449,7 +449,7 @@ local function start(cmd, cmd_args, dispatchers, extra_spawn_params)
       method = method;
       params = params;
     }
-    if result then
+    if result and message_callbacks then
       message_callbacks[message_id] = schedule_wrap(callback)
       return result, message_id
     else
@@ -548,14 +548,14 @@ local function start(cmd, cmd_args, dispatchers, extra_spawn_params)
           -- - The server will not send a result callback after this cancellation.
           -- - If the server sent this cancellation ACK after sending the result, the user of this RPC
           -- client will ignore the result themselves.
-          if result_id then
+          if result_id and message_callbacks then
             message_callbacks[result_id] = nil
           end
           return
         end
       end
 
-      local callback = message_callbacks[result_id]
+      local callback = message_callbacks and message_callbacks[result_id]
       if callback then
         message_callbacks[result_id] = nil
         validate {