undo-tree-enable-undo-in-region = nil

Try to save off the elusive and annoying "unrecognized entry in undo
list undo-tree-canary" error produced by undo-tree.

core/core-editor.el

@@ -183,9 +183,11 @@ fundamental-mode) for performance sake."
 (def-package! undo-tree
   :after-call (doom-exit-buffer-hook after-find-file)
   :config
-  ;; persistent undo history is known to cause undo history corruption, which
-  ;; can be very destructive! So disable it!
+  ;; persistent undo history and undo-in-region is known to cause undo history
+  ;; corruption, which can be very destructive! Disabling it deters the error,
+  ;; but does not fix it entirely!
   (setq undo-tree-auto-save-history nil
+        undo-tree-enable-undo-in-region nil
         undo-tree-history-directory-alist
         (list (cons "." (concat doom-cache-dir "undo-tree-hist/"))))
   (global-undo-tree-mode +1))

modules/config/default/+bindings.el

@@ -425,10 +425,6 @@
         (:map swiper-map
           [backtab]  #'+ivy/wgrep-occur))
 
-      ;; undo-tree -- undo/redo for visual regions
-      :v "C-u" #'undo-tree-undo
-      :v "C-r" #'undo-tree-redo
-
       ;; yasnippet
       (:after yasnippet
         (:map yas-keymap