Reuse alert dispatcher

Instead of using a specific alert handler in `SessionImpl::saveResumeData()`, reuse the generic
one.

src/base/bittorrent/sessionimpl.cpp

@@ -2444,6 +2444,12 @@ void SessionImpl::handleTorrentSaveResumeDataRequested(const TorrentImpl *torren
     ++m_numResumeData;
 }
 
+void SessionImpl::handleTorrentSaveResumeDataFailed(const TorrentImpl *torrent)
+{
+    Q_UNUSED(torrent);
+    --m_numResumeData;
+}
+
 QVector<Torrent *> SessionImpl::torrents() const
 {
     QVector<Torrent *> result;
@@ -2904,16 +2910,12 @@ void SessionImpl::saveResumeData()
         bool hasWantedAlert = false;
         for (const lt::alert *a : alerts)
         {
-            switch (a->type())
+            if (const int alertType = a->type();
+                (alertType == lt::save_resume_data_alert::alert_type)
+                || (alertType == lt::save_resume_data_failed_alert::alert_type))
             {
-            case lt::save_resume_data_failed_alert::alert_type:
                 hasWantedAlert = true;
-                --m_numResumeData;
-                break;
-            case lt::save_resume_data_alert::alert_type:
-                hasWantedAlert = true;
-                dispatchTorrentAlert(static_cast<const lt::torrent_alert *>(a));
-                break;
+                handleAlert(a);
             }
         }
 

src/base/bittorrent/sessionimpl.h

@@ -410,6 +410,7 @@ namespace BitTorrent
         // Torrent interface
         void handleTorrentNeedSaveResumeData(const TorrentImpl *torrent);
         void handleTorrentSaveResumeDataRequested(const TorrentImpl *torrent);
+        void handleTorrentSaveResumeDataFailed(const TorrentImpl *torrent);
         void handleTorrentShareLimitChanged(TorrentImpl *const torrent);
         void handleTorrentNameChanged(TorrentImpl *const torrent);
         void handleTorrentSavePathChanged(TorrentImpl *const torrent);

src/base/bittorrent/torrentimpl.cpp

@@ -1949,8 +1949,13 @@ void TorrentImpl::prepareResumeData(const lt::add_torrent_params &params)
 
 void TorrentImpl::handleSaveResumeDataFailedAlert(const lt::save_resume_data_failed_alert *p)
 {
-    Q_UNUSED(p);
-    Q_ASSERT_X(false, Q_FUNC_INFO, "This point should be unreachable since libtorrent 1.2.11");
+    if (p->error != lt::errors::resume_data_not_modified)
+    {
+        LogMsg(tr("Generate resume data failed. Torrent: \"%1\". Reason: \"%2\"")
+            .arg(name(), QString::fromLocal8Bit(p->error.message().c_str())), Log::CRITICAL);
+    }
+
+    m_session->handleTorrentSaveResumeDataFailed(this);
 }
 
 void TorrentImpl::handleFastResumeRejectedAlert(const lt::fastresume_rejected_alert *p)