AreaCom: Make YearFrom nullable

Elwig/Models/Entities/AreaCom.cs

@@ -32,7 +32,7 @@ namespace Elwig.Models.Entities {
         public int? RdNr { get; set; }
 
         [Column("year_from")]
-        public int YearFrom { get; set; }
+        public int? YearFrom { get; set; }
 
         [Column("year_to")]
         public int? YearTo { get; set; }