AreaCom: Make YearFrom nullable

Elwig/Helpers/AppDbUpdater.cs

@@ -9,7 +9,7 @@ namespace Elwig.Helpers {
     public static class AppDbUpdater {
 
         // Don't forget to update value in Tests/fetch-resources.bat!
-        public static readonly int RequiredSchemaVersion = 29;
+        public static readonly int RequiredSchemaVersion = 30;
 
         private static int VersionOffset = 0;