Fix crash when adding an ampty tracker URL

Changelog

@@ -4,6 +4,7 @@
   - BUGFIX: Disable OS cache for aligned files to reduce memory consumption
   - BUGFIX: Fix torrent upload from Web UI (Windows)
   - BUGFIX: Fix cursor problem in torrent addition dialog
+  - BUGFIX: Fix crash when additing an empty tracker URL
 
 * Tue Feb 8 2011 - Christophe Dumez <chris@qbittorrent.org> - v2.6.6 
   - FEATURE: IP address reported to trackers is now customizable

src/properties/trackerlist.cpp

@@ -295,6 +295,7 @@ void TrackerList::askForTrackers(){
   QStringList trackers = TrackersAdditionDlg::askForTrackers(h);
   if(!trackers.empty()) {
     foreach(const QString& tracker, trackers) {
+      if(tracker.trimmed().isEmpty()) continue;
       announce_entry url(tracker.toStdString());
       url.tier = 0;
       h.add_tracker(url);

src/properties/trackersadditiondlg.h

@@ -67,6 +67,7 @@ public:
 public slots:
   void on_uTorrentListButton_clicked() {
     downloadThread *d = new downloadThread(this);
+    uTorrentListButton->setEnabled(false);
     connect(d, SIGNAL(downloadFinished(QString,QString)), SLOT(parseUTorrentList(QString,QString)));
     connect(d, SIGNAL(downloadFailure(QString,QString)), SLOT(getTrackerError(QString,QString)));
     //Just to show that it takes times
@@ -79,6 +80,8 @@ public slots:
     if (!list_file.open(QFile::ReadOnly)) {
       QMessageBox::warning(this, tr("I/O Error"), tr("Error while trying to open the downloaded file."), QMessageBox::Ok);
       setCursor(Qt::ArrowCursor);
+      uTorrentListButton->setEnabled(true);
+      sender()->deleteLater();
       return;
     }
     QList<QUrl> existingTrackers;
@@ -114,16 +117,20 @@ public slots:
     list_file.remove();
     //To restore the cursor ...
     setCursor(Qt::ArrowCursor);
+    uTorrentListButton->setEnabled(true);
     // Display information message if necessary
     if(nb == 0) {
       QMessageBox::information(this, tr("No change"), tr("No additional trackers were found."), QMessageBox::Ok);
     }
+    sender()->deleteLater();
   }
 
-  void getTrackerError(QString, QString error) {
+  void getTrackerError(const QString&, const QString &error) {
     //To restore the cursor ...
     setCursor(Qt::ArrowCursor);
+    uTorrentListButton->setEnabled(true);
     QMessageBox::warning(this, tr("Download error"), tr("The trackers list could not be downloaded, reason: %1").arg(error), QMessageBox::Ok);
+    sender()->deleteLater();
   }
 
 public: