[LyX/2.2.x] Compile on debian bookworm.

[Pavel Sanda]

commit 1f79cfc044acfc2097ffaeb594ca78a103f1ecfe
Author: Pavel Sanda <sanda at lyx.org>
Date:   Sat Jul 11 03:28:42 2026 +0200

    Compile on debian bookworm.
---
 src/frontends/qt4/GuiDocument.cpp | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/frontends/qt4/GuiDocument.cpp b/src/frontends/qt4/GuiDocument.cpp
index 77a1e5f9e8..b0c25e043d 100644
--- a/src/frontends/qt4/GuiDocument.cpp
+++ b/src/frontends/qt4/GuiDocument.cpp
@@ -67,6 +67,7 @@
 #include "frontends/alert.h"
 
 #include <QAbstractItemModel>
+#include <QButtonGroup>
 #include <QHeaderView>
 #include <QColor>
 #include <QColorDialog>