title: Xcode's debugger is giving me <????> (question marks). What do I do?
body: <p>This is what I see when my app crashes (for no obvious reason, sometimes on startup, sometimes much later on).</p>
  
  <p>What on Earth can I do?</p>
  
  <p><img src="https://i.stack.imgur.com/h89ay.png" alt="Lots of questions marks in the Xcode debugger"></p>