Avoid rare errors in dabbrev.el

* lisp/dabbrev.el (dabbrev-expand, dabbrev--find-expansion): Make
sure 'dabbrev--last-buffer' is a live buffer before using its
value.  (Bug#70824)

1 files changed, 6 insertions, 5 deletions

diff --git a/lisp/dabbrev.el b/lisp/dabbrev.el
index 853c0f4b290..7b6cbb78cef 100644
--- a/lisp/dabbrev.el
+++ b/lisp/dabbrev.el
@@ -495,7 +495,7 @@ See also `dabbrev-abbrev-char-regexp' and \\[dabbrev-completion]."
               (save-excursion
                 (save-restriction
                   (widen)
-                  (if dabbrev--last-buffer
+                  (if (buffer-live-p dabbrev--last-buffer)
                       (set-buffer dabbrev--last-buffer))
                   ;; Find the end of the last "expansion" word.
                   (if (or (eq dabbrev--last-direction 1)
@@ -557,7 +557,8 @@ See also `dabbrev-abbrev-char-regexp' and \\[dabbrev-completion]."
             (setq dabbrev--last-buffer-found dabbrev--last-buffer))
         (message nil))
       (if (and (or (eq (current-buffer) dabbrev--last-buffer)
-                   (null dabbrev--last-buffer))
+                   (null dabbrev--last-buffer)
+                   (buffer-live-p dabbrev--last-buffer))
                (numberp dabbrev--last-expansion-location)
                (and (> dabbrev--last-expansion-location (point))))
           (setq dabbrev--last-expansion-location
@@ -731,7 +732,7 @@ of the start of the occurrence."
   (save-excursion
     ;; If we were scanning something other than the current buffer,
     ;; continue scanning there.
-    (when dabbrev--last-buffer
+    (when (buffer-live-p dabbrev--last-buffer)
       (set-buffer dabbrev--last-buffer))
     (or
      ;; ------------------------------------------
@@ -748,7 +749,7 @@ of the start of the occurrence."
      ;; or whatever buffer we were last scanning.
      ;; ------------------------------------------
      (and (or (not dabbrev-search-these-buffers-only)
-              dabbrev--last-buffer)
+              (buffer-live-p dabbrev--last-buffer))
           (<= direction 0)
           (setq dabbrev--last-direction -1)
           (dabbrev--try-find abbrev nil
@@ -760,7 +761,7 @@ of the start of the occurrence."
      ;; ------------------------------------------
      (progn
        (setq dabbrev--last-direction -1)
-       (unless dabbrev--last-buffer
+       (unless (buffer-live-p dabbrev--last-buffer)
          ;; If we have just now begun to search other buffers,
          ;; determine which other buffers we should check.
          ;; Put that list in dabbrev--friend-buffer-list.