additional check for checkoffs

PROMS/Volian.Controls.Library/EditItem.cs

@@ -182,7 +182,7 @@ namespace Volian.Controls.Library
 				if (VlnSettings.StepTypeToolType) SetToolTip(_MyItemInfo.ToolTip);
 				ChangeBar = _MyItemInfo.HasChangeBar;
 				CheckOff co = _MyItemInfo.GetCheckOffStep();
-				if (co != null)
+				if (co != null && co.UIMark != null)
 				{
 					UserCheckOff = true;
 					UserCheckOffChar = (char)co.UIMark;