> echo "Please make sure 'clangd' has installed!"
Sorry, but I don't have clangd installed either.
But let's try one thing first: IIUC 'winner-save-old-configurations' can
fail in the indicated way only if it tries to insert a dead frame. So
please try with the following trivial patch:
diff --git a/lisp/winner.el b/lisp/winner.el
index c8354b18be..9fd86ae23f 100644
--- a/lisp/winner.el
+++ b/lisp/winner.el
@@ -178,7 +178,8 @@ winner-save-old-configurations
(setq winner-last-frames nil)
(setq winner-last-command this-command))
(dolist (frame winner-modified-list)
- (winner-insert-if-new frame))
+ (when (frame-live-p frame)
+ (winner-insert-if-new frame)))
(setq winner-modified-list nil)
(winner-remember)))
I doubt it will help much but at least we can exclude one possible
source of troubles.
martin