[niepce/gtk4] gtk4: Fix about dialog

[Hubert Figuière <hub src gnome org>]

commit 34d8202db0160266910628e3bba4196fb57b1d4d
Author: Hubert Figuière <hub figuiere net>
Date:   Fri May 6 22:33:19 2022 -0400

    gtk4: Fix about dialog

 src/niepce/ui/niepceapplication.cpp | 19 +++++++++++--------
 1 file changed, 11 insertions(+), 8 deletions(-)
---
diff --git a/src/niepce/ui/niepceapplication.cpp b/src/niepce/ui/niepceapplication.cpp
index b48232f..b618bf6 100644
--- a/src/niepce/ui/niepceapplication.cpp
+++ b/src/niepce/ui/niepceapplication.cpp
@@ -70,17 +70,20 @@ void NiepceApplication::on_action_file_open()
 
 void NiepceApplication::on_about()
 {
-    Gtk::AboutDialog dlg;
+    DBG_OUT("on_about");
+    Gtk::AboutDialog* dlg = new Gtk::AboutDialog();
 //    dlg.set_name("Niepce");
-    dlg.set_program_name("Niepce Digital");
-    dlg.set_version(VERSION);
-    dlg.set_logo_icon_name("org.gnome.Niepce");
-    dlg.set_license_type(Gtk::License::GPL_3_0);
-    dlg.set_comments(Glib::ustring(_("A digital photo application.\n\n"
+    dlg->set_program_name("Niepce Digital");
+    dlg->set_version(VERSION);
+    dlg->set_logo_icon_name("org.gnome.Niepce");
+    dlg->set_license_type(Gtk::License::GPL_3_0);
+    dlg->set_comments(Glib::ustring(_("A digital photo application.\n\n"
                                      "Build options: ")) +
                      NIEPCE_BUILD_CONFIG);
-    dlg.set_transient_for(m_main_frame.lock()->gtkWindow());
-    dlg.show();
+    dlg->set_transient_for(m_main_frame.lock()->gtkWindow());
+    dlg->set_modal(true);
+    dlg->set_hide_on_close(true);
+    dlg->show();
 }
 
 void NiepceApplication::on_action_preferences()