Fix SQLite tests

Author: maca88

src/NHibernate.Test/NHSpecificTest/GH2029/Fixture.cs

@@ -1,6 +1,7 @@
 using System;
 using System.Linq;
 using NHibernate.Cfg.MappingSchema;
+using NHibernate.Dialect;
 using NHibernate.Mapping.ByCode;
 using NUnit.Framework;
 
@@ -33,6 +34,11 @@ protected override HbmMapping GetMappings()
 			return mapper.CompileMappingForAllExplicitlyAddedEntities();
 		}
 
+		protected override bool AppliesTo(Dialect.Dialect dialect)
+		{
+			return !(dialect is SQLiteDialect);
+		}
+
 		protected override void OnSetUp()
 		{
 			using (var session = OpenSession())

src/NHibernate/Linq/Visitors/HqlGeneratorExpressionVisitor.cs

@@ -270,7 +270,9 @@ protected HqlTreeNode VisitNhSum(NhSumExpression expression)
 			if (nhType != null && _parameters.SessionFactory.SQLFunctionRegistry.FindSQLFunction("sum")
 			                      ?.ReturnType(nhType, _parameters.SessionFactory)?.ReturnedClass == type)
 			{
-				return _hqlTreeBuilder.Sum(VisitExpression(expression.Expression).AsExpression());
+				return _hqlTreeBuilder.TransparentCast(
+					_hqlTreeBuilder.Sum(VisitExpression(expression.Expression).AsExpression()),
+					expression.Type);
 			}
 
 			return _hqlTreeBuilder.Cast(_hqlTreeBuilder.Sum(VisitExpression(expression.Expression).AsExpression()), expression.Type);