Clean up and fix possible corruption on missing bin clip id

Related to #533

src/bin/projectitemmodel.cpp

@@ -620,7 +620,7 @@ bool ProjectItemModel::requestAddFolder(QString &id, const QString &name, const
 {
     QWriteLocker locker(&m_lock);
     if (!id.isEmpty() && !isIdFree(id)) {
-        id = QString();
+        id.clear();
     }
     if (id.isEmpty()) {
         id = QString::number(getFreeFolderId());
@@ -641,7 +641,7 @@ bool ProjectItemModel::requestAddBinClip(QString &id, const QDomElement &descrip
             id = QString::number(getFreeClipId());
         }
     }
-    Q_ASSERT(!id.isEmpty() && isIdFree(id));
+    Q_ASSERT(isIdFree(id));
     qDebug() << "/////////// found id" << id;
     std::shared_ptr<ProjectClip> new_clip =
         ProjectClip::construct(id, description, m_blankThumb, std::static_pointer_cast<ProjectItemModel>(shared_from_this()));
@@ -683,7 +683,7 @@ bool ProjectItemModel::requestAddBinClip(QString &id, const std::shared_ptr<Mlt:
             id = QString::number(getFreeClipId());
         }
     }
-    Q_ASSERT(!id.isEmpty() && isIdFree(id));
+    Q_ASSERT(isIdFree(id));
     std::shared_ptr<ProjectClip> new_clip = ProjectClip::construct(id, m_blankThumb, std::static_pointer_cast<ProjectItemModel>(shared_from_this()), producer);
     bool res = addItem(new_clip, parentId, undo, redo);
     if (res) {
@@ -703,7 +703,7 @@ bool ProjectItemModel::requestAddBinSubClip(QString &id, int in, int out, const
     if (id.isEmpty()) {
         id = QString::number(getFreeClipId());
     }
-    Q_ASSERT(!id.isEmpty() && isIdFree(id));
+    Q_ASSERT(isIdFree(id));
     QString subId = parentId;
     if (subId.startsWith(QLatin1Char('A')) || subId.startsWith(QLatin1Char('V'))) {
         subId.remove(0, 1);
@@ -909,6 +909,9 @@ bool ProjectItemModel::loadFolders(Mlt::Properties &folders)
 bool ProjectItemModel::isIdFree(const QString &id) const
 {
     READ_LOCK();
+    if (id.isEmpty()) {
+        return false;
+    }
     for (const auto &clip : m_allItems) {
         auto c = std::static_pointer_cast<AbstractProjectItem>(clip.second.lock());
         if (c->clipId() == id) {

src/dialogs/renderwidget.cpp

@@ -1477,14 +1477,7 @@ void RenderWidget::generateRenderFiles(QDomDocument doc, const QString &playlist
         for (int i = 0; i < prods.count(); ++i) {
             auto prod = prods.at(i).toElement();
             if (prod.attribute(QStringLiteral("id")) == QStringLiteral("black_track")) {
-                auto props = prod.elementsByTagName(QStringLiteral("property"));
-                for (int j = 0; j < props.count(); ++j) {
-                    auto prop = props.at(j).toElement();
-                    if (prop.attribute(QStringLiteral("name")) == QStringLiteral("resource")) {
-                        prop.firstChild().setNodeValue(QStringLiteral("transparent"));
-                        break;
-                    }
-                }
+                Xml::setXmlProperty(prod, QStringLiteral("resource"), QStringLiteral("transparent"));
                 break;
             }
         }

src/mltcontroller/clipcontroller.cpp

@@ -134,6 +134,7 @@ void ClipController::addMasterProducer(const std::shared_ptr<Mlt::Producer> &pro
         qCDebug(KDENLIVE_LOG) << "// WARNING, USING INVALID PRODUCER";
     } else {
         checkAudioVideo();
+        setProducerProperty(QStringLiteral("kdenlive:id"), m_controllerBinId);
         QString proxy = m_properties->get("kdenlive:proxy");
         m_service = m_properties->get("mlt_service");
         QString path = m_properties->get("resource");
@@ -151,7 +152,6 @@ void ClipController::addMasterProducer(const std::shared_ptr<Mlt::Producer> &pro
         m_path = path.isEmpty() ? QString() : QFileInfo(path).absoluteFilePath();
         getInfoForProducer();
         emitProducerChanged(m_controllerBinId, producer);
-        setProducerProperty(QStringLiteral("kdenlive:id"), m_controllerBinId);
     }
     connectEffectStack();
 }
@@ -352,6 +352,7 @@ void ClipController::updateProducer(const std::shared_ptr<Mlt::Producer> &produc
     *m_masterProducer = producer.get();
     m_properties = new Mlt::Properties(m_masterProducer->get_properties());
     m_producerLock.unlock();
+    setProducerProperty(QStringLiteral("kdenlive:id"), m_controllerBinId);
     checkAudioVideo();
     // Pass properties from previous producer
     m_properties->pass_list(passProperties, passList);