Unsupported diff type on kactus 0.3.8 at Mac OS 10.12.6
## Description
My Kactus is showing a message on launch with title: **Kactus failed to launch**

The log Kactus is:
```Error: Unsupported diff type: [object Object]
    at Object.t.assertNever (/webpack:/renderer.js:1:1)
    at y.renderDiff (/webpack:/renderer.js:21:1)
    at y.render (/webpack:/renderer.js:21:1)
    at Ro (/webpack:/renderer.js:66:1)
    at R (/webpack:/renderer.js:66:1)
    at qo (/webpack:/renderer.js:66:1)
    at Yo (/webpack:/renderer.js:66:1)
    at cr (/webpack:/renderer.js:66:1)
    at sr (/webpack:/renderer.js:66:1)
    at ar (/webpack:/renderer.js:66:1)

Version: 0.3.8
OS: Mac OS 10.12.6```
