Fixes a race condition when initializing the calendar-event field

The problem was that the field executes a request to validate its
state. This was initiated at the same time for two values. Then it was
undetermined which value comes back first.

modules/webapp/src/main/elm/Comp/CalEventInput.elm

@@ -2,6 +2,7 @@ module Comp.CalEventInput exposing
     ( Model
     , Msg
     , init
+    , initDefault
     , update
     , view
     )
@@ -36,6 +37,11 @@ type Msg
     | CheckInputMsg CalEvent (Result Http.Error CalEventCheckResult)
 
 
+initDefault : Model
+initDefault =
+    Model Nothing
+
+
 init : Flags -> CalEvent -> ( Model, Cmd Msg )
 init flags ev =
     ( Model Nothing, checkInput flags ev )