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-rw-r--r--generic/proof.el8
1 files changed, 6 insertions, 2 deletions
diff --git a/generic/proof.el b/generic/proof.el
index d2aaff13..f56f577e 100644
--- a/generic/proof.el
+++ b/generic/proof.el
@@ -2169,8 +2169,12 @@ deletes the region corresponding to the proof sequence."
Unless optional NO-DELETE is set, the text is also deleted from
the proof script."
(interactive "p")
- (goto-char (span-start (span-at-before (proof-locked-end) 'type)))
- (proof-retract-until-point (not no-delete)))
+ (let ((lastspan (span-at-before (proof-locked-end) 'type)))
+ (if lastspan
+ (progn
+ (goto-char (span-start lastspan))
+ (proof-retract-until-point (not no-delete)))
+ (error "Nothing to undo!"))))
(defun proof-interrupt-process ()
(interactive)