Fix timeline preview invalidated by composition on project load.

Related to #1266

src/mainwindow.cpp

@@ -2352,6 +2352,8 @@ void MainWindow::connectDocument()
     
     // Load master effect zones
     getMainTimeline()->controller()->updateMasterZones(getMainTimeline()->controller()->getModel()->getMasterEffectZones());
+    // Connect stuff for timeline preview
+    connect(getMainTimeline()->controller()->getModel().get(), &TimelineModel::invalidateZone, getMainTimeline()->controller(), &TimelineController::invalidateZone, Qt::DirectConnection);
 
     m_buttonSelectTool->setChecked(true);
     connect(m_projectMonitorDock, &QDockWidget::visibilityChanged, m_projectMonitor, &Monitor::slotRefreshMonitor, Qt::UniqueConnection);

src/timeline2/view/timelinecontroller.cpp

@@ -123,7 +123,6 @@ void TimelineController::setModel(std::shared_ptr<TimelineItemModel> model)
     connect(this, &TimelineController::videoTargetChanged, this, &TimelineController::updateVideoTarget);
     connect(this, &TimelineController::audioTargetChanged, this, &TimelineController::updateAudioTarget);
     connect(m_model.get(), &TimelineItemModel::requestMonitorRefresh, [&]() { pCore->requestMonitorRefresh(); });
-    connect(m_model.get(), &TimelineModel::invalidateZone, this, &TimelineController::invalidateZone, Qt::DirectConnection);
     connect(m_model.get(), &TimelineModel::durationUpdated, this, &TimelineController::checkDuration);
     connect(m_model.get(), &TimelineModel::selectionChanged, this, &TimelineController::selectionChanged);
     connect(m_model.get(), &TimelineModel::selectedMixChanged, this, &TimelineController::showMixModel);