Uncaught TypeError: noflip expects a string or a number

[aroundus]

react-dates version
react-dates@21.8.0

Describe the bug
spacing.dayPickerHorizontalPadding is undefined.

Source code (including props configuration)
Steps to reproduce the behavior:

export default withStyles(({
  reactDates: {
    color,
    font,
    noScrollBarOnVerticalScrollable,
    spacing,
    zIndex,
  },
}) => ({
  ...

  DayPicker_weekHeaders__horizontal: {
    marginLeft: noflip(spacing.dayPickerHorizontalPadding), // undefined
  },

  ...
}), { pureComponent: typeof React.PureComponent !== 'undefined' })(DayPicker);

Screenshots/Gifs

Additional context
It works normally in production environment. Problem exists only in development environment.

[ljharb]

It shouldn't be working in either one. You can't call noflip with undefined.

Try spacing.dayPickerHorizontalPadding != null && noflip(spacing.dayPickerHorizontalPadding)