Bulk operations: Fixed update operation for Firebird

Author: alex-kulakov

Extensions/Xtensive.Orm.BulkOperations/Internals/SetOperation.cs

@@ -98,6 +98,9 @@ private void AddComputedStaticExpression(AddValueContext addContext)
       QueryTranslationResult request = parent.GetRequest(parent.QueryProvider.CreateQuery<T>(selectExpression));
       var sqlSelect = ((SqlSelect)request.Query);
       SqlExpression ex = sqlSelect.OrderBy[0].Expression;
+      if (ex is SqlCast sqlCast) {
+        ex = sqlCast.Operand;
+      }
       var placeholder = ex as SqlPlaceholder;
       if (placeholder == null)
       {