title: No protocol method defined for type object: :empty
body: <p>I'm trying to fix a bug in a Clojurescript frontend using Reagent and Re-frame. I find the error messages a little difficult to decipher at times and I can't crack this one.</p>
  <p>All I know is that I'm getting a bug in a particular view like this:</p>
  <p><code>No protocol method IAssociative.-assoc defined for type object: :empty</code></p>
  <p>I'm going to take a wild guess that I'm trying to assoc something with the type <code>:empty</code>. What kind of data would have a type of <code>:empty</code>?</p>
  <p>Am I at least on the right track? What sorts of things could raise an exception like this?</p>
  <p>This is what my stack trace looks like:</p>
  <p><a href="https://i.stack.imgur.com/SimTC.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/SimTC.png" alt="enter image description here" /></a></p>