#140 fixed NRE issue when ordering (#142)

Co-authored-by: Emrah Kondur <emrah.kondur@invicti.com>

Author: ekondur

DatatableJS.Net/Builders/OrderBuilder.cs

@@ -35,7 +35,7 @@ public OrderBuilder<T> Add<TProp>(Expression<Func<T, TProp>> property, OrderBy o
             var propertyName = ExpressionHelpers<T>.PropertyName(property);
 
             var column = _grid._columns
-                .Where(c => c.Data.Equals(propertyName))
+                .Where(c => c.Data != null && c.Data.Equals(propertyName))
                 .FirstOrDefault();
 
             if (column == null)

DatatableJS/Builders/OrderBuilder.cs

@@ -35,7 +35,7 @@ public OrderBuilder<T> Add<TProp>(Expression<Func<T, TProp>> property, OrderBy o
             var propertyName = ExpressionHelpers<T>.PropertyName(property);
 
             var column = _grid._columns
-                .Where(c => c.Data.Equals(propertyName))
+                .Where(c => c.Data != null && c.Data.Equals(propertyName))
                 .FirstOrDefault();
 
             if (column == null)