Fix wrong slot name

src/mainwindow.cpp

@@ -98,7 +98,7 @@ MainWindow::MainWindow(QWidget *parent, QStringList torrentCmdLine) : QMainWindo
   setWindowTitle(tr("qBittorrent %1", "e.g: qBittorrent v0.x").arg(QString::fromUtf8(VERSION)));
   displaySpeedInTitle = pref.speedInTitleBar();
   // Clean exit on log out
-  connect(static_cast<SessionApplication*>(qApp), SIGNAL(sessionIsShuttingDown()), this, SLOT(deleteQBtSession::instance()()));
+  connect(static_cast<SessionApplication*>(qApp), SIGNAL(sessionIsShuttingDown()), this, SLOT(deleteBTSession()));
   // Setting icons
   this->setWindowIcon(QIcon(QString::fromUtf8(":/Icons/skin/qbittorrent32.png")));
   actionOpen->setIcon(QIcon(QString::fromUtf8(":/Icons/skin/open.png")));