TypeError: undefined is not an object (evaluating 'Function.prototype.toString')
I am reporting a bug or issue - I can't get any of the examples to run. They all produce the same error.

**Expected behavior:**
Renders the "basic setup" example.

**Observed behavior:**
Produces error:
```
> npm run render

> basic-setup@1.0.0 render /Users/alampros/tmp/react-sketchapp/examples/basic-setup
> skpm build --watch --run

🖨  Copied src/manifest.json in 3ms
TypeError: undefined is not an object (evaluating 'Function.prototype.toString')
line: 707
stack: isNative


__webpack_require__


__webpack_require__


__webpack_require__


__webpack_require__

__webpack_require__

__webpack_require__

run
run@[native code]
column: 40
⚒  Built ./my-command.js in 900ms
```

**How to reproduce:**
Follow the steps in the README:
```sh
git clone https://github.com/airbnb/react-sketchapp.git
cd react-sketchapp/examples/basic-setup && npm install

npm run render
```

**Sketch version:** 47.1 (45422)

