Chokes on nested classNames & media queries containing variables

**Describe the bug**
Seems to break when formatting both nested class names and also media queries containing variables.

**To Reproduce**
```
  export const Div = styled.div`
    .wordmark {
      @media screen and (max-width: ${getMediumBreakpoint}px) {
        display: none;
      }
    }
  `;
```