chatgui: QPointer-защита при генерации превью в фоне

tools/chatgui/src/messagelist.cpp

@@ -19,6 +19,7 @@
 #include <QFile>
 #include <QScrollBar>
 #include <QApplication>
+#include <QPointer>
 #include <QDebug>
 #include <QFileInfo>
 #include <QFile>
@@ -749,13 +750,16 @@ void MessageList::onAttachmentDownloaded(const QString& chId, int64_t msgId) {
         QString fp = item->data(MsgVoiceFileRole).toString();
         QString thumbPath = fp + ".jpg";
         if (!fp.isEmpty() && QFile::exists(fp) && !QFile::exists(thumbPath)) {
-            std::thread([this, fp, thumbPath]() {
+            QPointer<MessageList> self(this);
+            std::thread([self, fp, thumbPath]() {
                 int rc = video_extract_thumbnail(fp.toUtf8().constData(),
                                                  thumbPath.toUtf8().constData(), 320);
                 DEBUG_DEBUG(DEBUG_CATEGORY_VIDEO, "MessageList: thumbnail %s rc=%d",
                             qPrintable(thumbPath), rc);
-                QMetaObject::invokeMethod(this, [this]() { m_view->viewport()->update(); },
-                                          Qt::QueuedConnection);
+                if (self) {
+                    QMetaObject::invokeMethod(self, [self]() { self->m_view->viewport()->update(); },
+                                              Qt::QueuedConnection);
+                }
             }).detach();
         }
     }