Problem resolving associated promise models in ember inspector 3.3.1

The model click in works now post 3.3.1 however if you try to resolve an association that is a promise in the inspector you get the following:

```
This is likely a bug in the inspector itself.
You can report bugs at https://github.com/emberjs/ember-inspector.
Error message: this.eachAttribute is not a function
Stack trace: TypeError: this.eachAttribute is not a function
at Proxy._debugInfo (/assets/vendor.js:157311:10)
at getDebugInfo (:3360:47)
at Class.mixinsForObject (:2993:23)
at Class.digIntoObject (:2869:28)
at Class.digDeeper (:2760:14)
at sendEvent (/assets/vendor.js:45855:14)
at Class.trigger (/assets/vendor.js:61035:33)
at wrap (:3462:14)
at Class. (:3492:18)
at Backburner._run (/assets/vendor.js:33021:35)
```

https://github.com/emberjs/ember-inspector/commit/194a035e2ebc43deb87a3b96321b08e3457025f3