[LyX/master] Qt4 compil fix

[Pavel Sanda]

commit 4e2f8dbbebf797f749c53b09b1a4d5a2c1e38cbc
Author: Pavel Sanda <sanda at lyx.org>
Date:   Tue Mar 16 09:39:05 2021 +0100

    Qt4 compil fix
---
 src/frontends/qt/IconPalette.cpp |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/src/frontends/qt/IconPalette.cpp b/src/frontends/qt/IconPalette.cpp
index 8956a48..580b450 100644
--- a/src/frontends/qt/IconPalette.cpp
+++ b/src/frontends/qt/IconPalette.cpp
@@ -27,7 +27,9 @@
 #include <QStyleOptionFrame>
 #include <QMouseEvent>
 #include <QVBoxLayout>
+#if QT_VERSION >= 0x060000
 #include <QWindow>
+#endif
 
 namespace lyx {
 namespace frontend {