fixed

Controllers/building_four.Controller.cs

@@ -225,10 +225,11 @@ namespace rmutr_report.Controllers
                 }
             }
 
+            if (building_fours.expense_category!=null)
+            {
                 foreach (var expense in building_fours.expense_category)
                 {
-                if (expense!=null)
-                {
+                
                     var a = building_fours.expense_category.Where(d => d.amount == d.amount)
                         .Sum(o => o.amount);
                     building_fours.total_expense = a;