Functions do not work with arrays

It works:

```jsx
const MyComp = styled('div')({
border: [2, 'solid', 'white'],
});
```
This does not work:

```jsx
const MyComp = styled('div')({
border: ({ children }) => !children && [2, 'solid', 'white'],
});
```

Works:

```jsx
const MyComp = styled('div')({
border: ({ children }) => !children && ['2px', 'solid', 'white'].join(' '),
});
```

Reproduce the two styled('div') examples from the issue and trace how direct style arrays differ from arrays returned by a function-valued style. The issue does not name a source file or test; done means the function form accepts the same array value as the direct form, with coverage for the reported examples.

Written by the indexing model from the issue text.