Fix audio mixer track effects applied twice when reopening project, leading to incorrect volume.

Fixes #792

src/audiomixer/mixerwidget.cpp

@@ -200,7 +200,7 @@ void MixerWidget::buildUI(Mlt::Tractor *service, const QString &trackTag)
             m_monitorFilter->set("disable", 0);
         } else if (filterService == QLatin1String("volume")) {
             m_levelFilter = fl;
-            int volume = m_levelFilter->get_int("level");
+            double volume = m_levelFilter->get_double("level");
             m_volumeSpin->setValue(volume);
             m_volumeSlider->setValue(fromDB(volume));
         } else if (filterService == QLatin1String("panner")) {

src/effects/effectstack/model/effectstackmodel.cpp

@@ -916,7 +916,8 @@ void EffectStackModel::importEffects(const std::weak_ptr<Mlt::Service> &service,
         int imported = 0;
         for (int i = 0; i < max; i++) {
             std::unique_ptr<Mlt::Filter> filter(ptr->filter(i));
-            if (filter->get_int("internal_added") > 0) {
+            if (filter->get_int("internal_added") > 0 && m_ownerId.first != ObjectType::TimelineTrack) {
+                // Required to load master audio effects
                 if (auto ms = m_masterService.lock()) {
                     ms->attach(*filter.get());
                 }