B2021-067: Null reference crash when printing procedure with all sections set to not applicable.

PROMS/Volian.Print.Library/PromsPrinter.cs

@@ -2619,6 +2619,7 @@ namespace Volian.Print.Library
 		}
 		private void LoadSectionTree(ItemInfo ii)
 		{
+			if (ii.Sections == null) return;		// B2021-067 crash on null reference
 			foreach (SectionInfo si in ii.Sections)
 			{
 				if (si.IsStepSection)