title: Adding two core data derived attributes on an entity causes crash when adding object to that entity
body: <p>I am trying to add derived attributes, introduced in iOS 13, to an app. The issue arises when creating a new version of the <code>xcdatamodel</code> with two new attributes in Entity A. Each of those attributes is a boolean, and is set as <code>derived</code> and <code>optional</code>. Each references an <code>optional</code> boolean on Entity B. None of the attributes on either entity is set as <code>scalar</code>. For each new derived attribute the derivation is basically a simple, to-one keypath to an object on Entity B. When I add just one of the new attributes - either one - the app functions fine. As soon as I add another attribute, the app crashes on inserting a new object into Entity A. Expanding on this, I find that adding more than one derived attribute at all to any entity is causing a crash upon inserting a new object into that entity. </p>
  
  <p>The error is simply </p>
  
  <blockquote>
    <p>Thread 1: signal SIGABRT</p>
  </blockquote>
  
  <p>with no reason given.</p>
  
  <p>This seems like crazy behavior to me. I can't find anyone else having a similar issue. Is this expected behavior for Core Data in iOS 13?</p>