Restore source objects when canceled

MatterControlLib/PartPreviewWindow/View3D/Actions/CombineObject3D_2.cs

@@ -129,6 +129,22 @@ namespace MatterHackers.MatterControl.PartPreviewWindow.View3D
 					try
 					{
 						Combine(cancellationTokenSource.Token, reporter);
+
+						if (cancellationToken.IsCancellationRequested)
+                        {
+							// the combine was canceled set our children to the source object children
+							SourceContainer.Visible = true;
+							RemoveAllButSource();
+							Children.Modify((list) =>
+							{
+								foreach (var child in SourceContainer.Children)
+								{
+									list.Add(child);
+								}
+							});
+
+							SourceContainer.Visible = false;
+						}
 					}
 					catch
 					{

Submodules/agg-sharp

@@ -1 +1 @@
-Subproject commit 1d16b11a1d3eb375996808be4ae174e98600edf6
+Subproject commit 4ecb3ed94a016319fb137e9f6b938c12bc7d6703