Filter dead buffers from persp-mode workspaces

Fix #4196
Fix #1525

modules/ui/workspaces/config.el

@@ -142,6 +142,14 @@ stored in `persp-save-dir'.")
           (cadr prev-buffers)
         head)))
 
+  ;; HACK Fixes #4196, #1525: selecting deleted buffer error when quitting Emacs
+  ;;      or on some buffer listing ops.
+  (defadvice! +workspaces-remove-dead-buffers-a (persp)
+    :before #'persp-buffers-to-savelist
+    (when (persp-p persp)
+      (setf (persp-buffers persp)
+            (cl-delete-if-not #'persp-get-buffer-or-null (persp-buffers persp)))))
+
   ;; Delete the current workspace if closing the last open window
   (define-key! persp-mode-map
     [remap delete-window] #'+workspace/close-window-or-workspace