From: Jean-Marc Lasgouttes <lasgouttes@lyx.org>
Date: Fri, 1 Jun 2018 19:48:26 +0000 (+0200)
Subject: Fixup c7496a11: test emptiness before accessing elements
X-Git-Tag: lyx-2.4.0dev-acb2ca7b~3381
X-Git-Url: https://git.lyx.org/gitweb/?a=commitdiff_plain;h=4d0c43f9aa944649d4b5788c5de98d37c280a036;p=lyx.git

Fixup c7496a11: test emptiness before accessing elements
---

diff --git a/src/Undo.cpp b/src/Undo.cpp
index c0cf56925e..693008268a 100644
--- a/src/Undo.cpp
+++ b/src/Undo.cpp
@@ -612,7 +612,9 @@ void Undo::endUndoGroup(CursorData const & cur_after)
 
 bool Undo::activeUndoGroup() const
 {
-	return d->group_level_ > 0 && d->undostack_.top().group_id == d->group_id_;
+	return d->group_level_ > 0
+		&& !d->undostack_.empty()
+		&& d->undostack_.top().group_id == d->group_id_;
 }