fixing undefined check on quaternion's setFromEuler

Hi,

While updating Cannon.js fps demo from r51 to r59, I found this error on setFromEuler. Quick js console explaining it:

```javascript
euler = {}
> Object {}
typeof euler['order']
> "undefined"
typeof euler['order'] === undefined
> false
typeof euler['order'] === "undefined"
> true
```

Cheers.