message: Fix withPropTypes with no info parameter
diff: @@ -8,5 +8,5 @@ import { Renderable, RenderFunction } from '@storybook/react'
  */
  export const withPropTypes = (info?: string) =>
  (story: RenderFunction, context: { kind: string, story: string }): Renderable => {
  - return (withInfo(`<div>${info}</div>`)(story) as any)(context)
  + return (withInfo(info && `<div>${info}</div>`)(story) as any)(context)
  }
  