core: sync display variables from struct preferences when ssrf terminates

Add qPrefDisplay sync to sync in SettingsObjectWrapper.

If a program part change display variables in struct preferences, they would
not be saved on disk.

Signed-off-by: Jan Iversen <jani@apache.org>

core/subsurface-qt/SettingsObjectWrapper.cpp

@@ -2351,6 +2351,8 @@ void SettingsObjectWrapper::load()
 
 void SettingsObjectWrapper::sync()
 {
+	qPrefDisplay::instance()->sync();
+
 	QSettings s;
 	s.beginGroup("Planner");
 	s.setValue("last_stop", prefs.last_stop);