Fix to dynamicdatagrid checking column is null

InABox.DynamicGrid/DynamicDataGrid.cs

@@ -478,7 +478,7 @@ namespace InABox.DynamicGrid
             if (!columns.Any())
                 GenerateColumns(columns); //override this to provide specific columns on startup
 
-            var removes = columns.Where(x => DatabaseSchema.Property(typeof(TEntity), x.ColumnName) == null || GetColumnEditor(x) is NullEditor)
+            var removes = columns.Where(x => x is null || DatabaseSchema.Property(typeof(TEntity), x.ColumnName) == null || GetColumnEditor(x) is NullEditor)
                .ToArray();
             foreach (var remove in removes)
                 columns.Remove(remove);