'Tis the fix to be simple (TODO: test, unit test?)

Change-Id: I2a612b43398e519539f37c20955fb4875fe8ce15

Author: papeh

Src/Common/Controls/XMLViews/XmlBrowseViewBaseVc.cs

@@ -597,7 +597,7 @@ internal int ListItemsClass
 		/// <returns>True if we can't prove the column is invalid</returns>
 		internal bool IsValidColumnSpec(XmlNode node)
 		{
-			List<XmlNode> possibleColumns = ComputePossibleColumns();
+			return PossibleColumnSpecs.Contains(node);
 			//// first, check to see if we can find some part or child node information
 			//// to process. Eg. Custom field column nodes that refer to parts that no longer exist
 			//// because the custom field has been removed so the parts cannot be generated
@@ -610,7 +610,7 @@ internal bool IsValidColumnSpec(XmlNode node)
 			//bool badReversalIndex = CheckForBadReversalIndex(possibleColumns, node);
 			//if (badReversalIndex)
 			//	return false;
-			return true;	// valid as far as we can tell.
+			//return true;	// valid as far as we can tell.
 		}
 
 		/// <summary>