Avoid using deprecated stats_alert

From libtorrent doc:
This alert has been superseded by calling post_torrent_updates() regularly on the session object.

src/base/bittorrent/session.cpp

@@ -386,7 +386,6 @@ Session::Session(QObject *parent)
                     | lt::alert::status_notification
                     | lt::alert::ip_block_notification
                     | lt::alert::performance_warning
-                    | lt::alert::stats_notification
                     | lt::alert::file_progress_notification;
 
     const std::string peerId = lt::generate_fingerprint(PEER_ID, QBT_VERSION_MAJOR, QBT_VERSION_MINOR, QBT_VERSION_BUGFIX, QBT_VERSION_BUILD);
@@ -4280,12 +4279,15 @@ void Session::handleStateUpdateAlert(const lt::state_update_alert *p)
 {
     for (const lt::torrent_status &status : p->status) {
         TorrentHandle *const torrent = m_torrents.value(status.info_hash);
-        if (torrent)
+
+        if (!torrent)
+            continue;
+
         torrent->handleStateUpdate(status);
     }
 
     m_torrentStatusReport = TorrentStatusReport();
-    for (TorrentHandle *const torrent : asConst(m_torrents)) {
+    for (const TorrentHandle *torrent : asConst(m_torrents)) {
         if (torrent->isDownloading())
             ++m_torrentStatusReport.nbDownloading;
         if (torrent->isUploading())

src/base/bittorrent/torrenthandle.cpp

@@ -1799,14 +1799,6 @@ void TorrentHandle::handleFileCompletedAlert(const lt::file_completed_alert *p)
     }
 }
 
-void TorrentHandle::handleStatsAlert(const lt::stats_alert *p)
-{
-    Q_ASSERT(p->interval >= 1000);
-    const SpeedSample transferred(p->transferred[lt::stats_alert::download_payload] * 1000LL / p->interval,
-            p->transferred[lt::stats_alert::upload_payload] * 1000LL / p->interval);
-    m_speedMonitor.addSample(transferred);
-}
-
 void TorrentHandle::handleMetadataReceivedAlert(const lt::metadata_received_alert *p)
 {
     Q_UNUSED(p);
@@ -1862,9 +1854,6 @@ void TorrentHandle::handleAppendExtensionToggled()
 void TorrentHandle::handleAlert(const lt::alert *a)
 {
     switch (a->type()) {
-    case lt::stats_alert::alert_type:
-        handleStatsAlert(static_cast<const lt::stats_alert*>(a));
-        break;
     case lt::file_renamed_alert::alert_type:
         handleFileRenamedAlert(static_cast<const lt::file_renamed_alert*>(a));
         break;
@@ -2013,6 +2002,9 @@ void TorrentHandle::updateStatus(const lt::torrent_status &nativeStatus)
         m_unchecked = false;
     else if (isDownloading())
         m_unchecked = true;
+
+    m_speedMonitor.addSample({nativeStatus.download_payload_rate
+        , nativeStatus.upload_payload_rate});
 }
 
 void TorrentHandle::setRatioLimit(qreal limit)

src/base/bittorrent/torrenthandle.h

@@ -368,7 +368,6 @@ namespace BitTorrent
         void handlePerformanceAlert(const lt::performance_alert *p) const;
         void handleSaveResumeDataAlert(const lt::save_resume_data_alert *p);
         void handleSaveResumeDataFailedAlert(const lt::save_resume_data_failed_alert *p);
-        void handleStatsAlert(const lt::stats_alert *p);
         void handleStorageMovedAlert(const lt::storage_moved_alert *p);
         void handleStorageMovedFailedAlert(const lt::storage_moved_failed_alert *p);
         void handleTorrentCheckedAlert(const lt::torrent_checked_alert *p);