[LyX/master] #10346 Amend change 01b2893f8b to make Qt4 compilable - again

[Stephan Witt]

commit 63fcb7b8e19432973e10ad4e253fbe9d59d8e3af
Author: Stephan Witt <switt at lyx.org>
Date:   Thu Aug 13 10:26:44 2020 +0200

    #10346 Amend change 01b2893f8b to make Qt4 compilable - again
---
 src/frontends/qt/qt_helpers.cpp |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/src/frontends/qt/qt_helpers.cpp b/src/frontends/qt/qt_helpers.cpp
index 8225b91..9d44c3f 100644
--- a/src/frontends/qt/qt_helpers.cpp
+++ b/src/frontends/qt/qt_helpers.cpp
@@ -47,6 +47,7 @@
 #include <QTextLayout>
 #include <QTextDocument>
 #include <QToolTip>
+#include <QUrl>
 
 #include <algorithm>
 #include <fstream>