Smart Knobs doesn't work with custom decorators #47

I have a decorator like this...

export const myDecorator = storyFn => { return <Card>{storyFn()}</Card>; };

The <Card> seems to break it. This is from Material UI. It doesn't seem to be Material UI though being the issue, since even just adding a simple <div> wrapper breaks it too. Smart knobs works fine on components without any custom decorators. Once I add it, no props show up in the Knobs panel.

.addDecorator(myDecorator)

Any idea why? Thanks.