Fix torrent addition dialog geometry saving

When switching between single-file and multi-file torrents, the
dialog geometry saving / loading code was not behaving correctly.
(cherry picked from commit 443f693acf)

src/torrentadditiondlg.h

@@ -91,6 +91,7 @@ private:
   bool is_magnet;
   int hidden_height;
   QStringList path_history;
+  bool m_showContentList;
 };
 
 #endif