fix crash on document open.

Related to #1571

src/doc/kdenlivedoc.cpp

@@ -370,10 +370,11 @@ void KdenliveDoc::initializeProperties(bool newDocument)
     }
 }
 
-const QStringList KdenliveDoc::guidesCategories() const
+const QStringList KdenliveDoc::guidesCategories()
 {
     if (!m_documentProperties.contains(QStringLiteral("guidesCategories")) || m_documentProperties.value(QStringLiteral("guidesCategories")).isEmpty()) {
-        return getDefaultGuideCategories();
+        const QString defaultCategories = getDefaultGuideCategories().join(QLatin1Char('\n'));
+        m_documentProperties[QStringLiteral("guidesCategories")] = defaultCategories;
     }
     return m_documentProperties.value(QStringLiteral("guidesCategories")).split(QLatin1Char('\n'));
 }
@@ -1548,8 +1549,7 @@ void KdenliveDoc::loadDocumentProperties()
     if (!profileFound) {
         qDebug() << "ERROR, no matching profile found";
     }
-    const QStringList guideCategories = m_documentProperties.value(QStringLiteral("guidesCategories")).split(QLatin1Char('\n'));
-    m_guideModel->loadCategories(guideCategories);
+    m_guideModel->loadCategories(guidesCategories());
     updateProjectProfile(false);
 }
 

src/doc/kdenlivedoc.h

@@ -216,7 +216,7 @@ public:
     /** @brief Ensure we don't have leftover preview chunks (created after last save */
     void cleanupTimelinePreview(const QDateTime &documentDate);
     /** @brief Returns the guides categories for the project in format {name:index:#color} */
-    const QStringList guidesCategories() const;
+    const QStringList guidesCategories();
     /** @brief Set the guides categories for the project in format {name:index:#color} */
     void updateGuideCategories(const QStringList &categories, const QMap<int, int> remapCategories = {});
     /** @brief Setup a filter to visible guides */

src/project/dialogs/guideslist.cpp

@@ -339,6 +339,10 @@ void GuidesList::setModel(std::weak_ptr<MarkerListModel> model, std::shared_ptr<
 
 void GuidesList::rebuildCategories()
 {
+    if (pCore->markerTypes.isEmpty()) {
+        // Categories are not ready, abort
+        return;
+    }
     QPixmap pixmap(32, 32);
     // Cleanup default marker category menu
     QMenu *markerDefaultMenu = default_category->menu();