Don't leave dangling pointers to old document when importing.

This goes for both selection pointers and undo/redo pointers.

Fixes https://gitlab.com/kicad/code/kicad/issues/10145

eeschema/files-io.cpp

@@ -632,6 +632,10 @@ void SCH_EDIT_FRAME::OnImportProject( wxCommandEvent& aEvent )
     if( dlg.ShowModal() == wxID_CANCEL )
         return;
 
+    // Don't leave dangling pointers to previously-opened document.
+    m_toolManager->GetTool<EE_SELECTION_TOOL>()->ClearSelection();
+    ClearUndoRedoList();
+
     if( setProject )
     {
         Schematic().SetProject( nullptr );
@@ -665,8 +669,6 @@ void SCH_EDIT_FRAME::OnImportProject( wxCommandEvent& aEvent )
         return;
     }
 
-    m_toolManager->GetTool<EE_SELECTION_TOOL>()->ClearSelection();
-
     importFile( dlg.GetPath(), pluginType );
 
     RefreshCanvas();