Free item memory when closing schematic window

This fires the dtor for each item on the screen, allowing us to properly
close and remove them from the connection graph

Fixes https://gitlab.com/kicad/code/kicad/-/issues/17961

eeschema/sch_edit_frame.cpp

@@ -1097,7 +1097,7 @@ void SCH_EDIT_FRAME::doCloseWindow()
     if( !Schematic().GetFileName().IsEmpty() && !Schematic().RootScreen()->IsEmpty() )
         UpdateFileHistory( fileName );
 
-    Schematic().RootScreen()->Clear();
+    Schematic().RootScreen()->Clear( true );
 
     // all sub sheets are deleted, only the main sheet is usable
     GetCurrentSheet().clear();