[GTKUI] Only save_state when mainwindow is visible

* A similar fix (550ddc01) was applied to develop so backporting to guard
   against similar problems with columns not saving properly.

deluge/ui/gtkui/torrentview.py

@@ -350,14 +350,14 @@ class TorrentView(listview.ListView, component.Component):
 
     def shutdown(self):
         """Called when GtkUi is exiting"""
-        if self.window.visible():
-            self.save_state()
+        self.save_state()
 
     def save_state(self):
         """
         Saves the state of the torrent view.
         """
-        listview.ListView.save_state(self, "torrentview.state")
+        if self.window.visible():
+            listview.ListView.save_state(self, "torrentview.state")
 
     def remove_column(self, header):
         """Removes the column with the name 'header' from the torrentview"""