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)

(cherry picked from commit 5f3f461cd0c76b1b171bb9eda3db1f561bc22b80)

diff --git a/lisp/dabbrev.el b/lisp/dabbrev.el
index 6305540f691ee0739ae92542f612b559d7f9988c..b12f8c1ac7732864e118246d53a4a55f29f09bd2 100644 (file)
--- 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.