Fix crash if report data source is an empty collection and sum() is used

src/AddIns/Misc/Reporting/ICSharpCode.Reporting/Src/PageBuilder/DataPageBuilder.cs

@@ -66,7 +66,6 @@ namespace ICSharpCode.Reporting.PageBuilder
 		void BuildDetail()
 		{
 			CurrentSection = ReportModel.DetailSection;
-			if(DataSourceContainsData()) {
 			CurrentLocation = DetailStart;
 			var converter = new ContainerConverter(DetailStart);
 			if (IsGrouped()) {
@@ -75,7 +74,6 @@ namespace ICSharpCode.Reporting.PageBuilder
 				BuildSortedDetails(converter,DetailStart);
 			}
 		}
-		}
 
 
 		void BuildGroupedDetails (IContainerConverter converter,Point startPosition) {
@@ -194,18 +192,8 @@ namespace ICSharpCode.Reporting.PageBuilder
 		
 		void CreateDataSource(){
 			DataSource = new CollectionDataSource(List, ReportModel.ReportSettings);
-			if (DataSourceContainsData()) {
 			DataSource.Bind();
 		}
-		}
-		
-		
-		bool DataSourceContainsData () {
-			if (DataSource.Count > 0) {
-				return true;
-			}
-			return false;
-		}
 		
 		
 		static void AdjustLocationInSection(Point sectionPosition,List<IExportColumn> convertedItems)