fix not permitted parameter type (#117)

Author: corina-rusu

Ringhel.Procesio.Action.Core/ActionDecorators/FEDecoratorAttribute.cs

@@ -55,15 +55,15 @@ public class FEDecoratorAttribute : Attribute
     /// Properties with the same RowId will be ordered by their ColumnId value.
     /// If not set, properties will be displayed on different rows.
     /// </summary>
-    public int? ColumnId { get; set; }
+    public int ColumnId { get; set; } = 0;
 
     /// <summary>
     /// Property Column size. Used when displaying more than one property on the same row.
     /// Uses a 12-column grid system where the sum of all ColumnSize values on the same row should equal 12.
     /// For example: two properties can use sizes 3 and 9, or 6 and 6, or 4 and 8, etc.
     /// If not set, properties sharing the same row will be split equally.
     /// </summary>
-    public int? ColumnSize { get; set; }
+    public int ColumnSize { get; set; } = 0;
 
     /// <summary>
     /// Tooltip property.