fix ThreadRunner with empty TableColumn

Modules.Interfaces/ZUGFeRDInterface/PropertyValues.vb

@@ -54,6 +54,7 @@ Public Class PropertyValues
         ' Iterate through groups to get group scope and group items
         For Each oGroup In oGroupedProperties
             Dim oGroupScope As String = oGroup.Key
+
             Dim oPropertyList As New Dictionary(Of XmlItemProperty, List(Of Object))
             Dim oRowCount = 0
 
@@ -117,7 +118,7 @@ Public Class PropertyValues
                         oPropertyValue = String.Empty
                     End If
 
-                    _logger.Debug("ItemSpecification  [{0}] has value '{1}'", oTableColumn, oPropertyValue)
+                    _logger.Debug("ItemSpecification [{0}] has value '{1}'", oTableColumn, oPropertyValue)
 
                     oResult.ValidProperties.Add(New ValidProperty() With {
                         .MessageId = MessageId,