component inspector: mergings.indexOf is not a function

Ember inspector is choking when opening the components tab. Does this error look familiar? Any tips if it is due to misconfiguration of my app?

```
Uncaught TypeError: mergings.indexOf is not a function
at addNormalizedProperty (vendor.js:26525)
at mergeMixins (vendor.js:26568)
at applyMixin (vendor.js:26640)
at Class.reopen (vendor.js:38658)
at Class.retainObject (:2949:16)
at Class.retainObject (:4642:42)
at exports.default.inspectComponent (:1518:27)
at :1329:34
at Array.forEach ()
at exports.default.componentsForController (:1321:18)
```

After it throws the error on the component tab, if I clear the console long and toggle back to say "routes" or "data", then back to components, it doesn't throw the error any longer and the components tab works.

Ember inspector version
3.8.0

App version: 3.8.1