Keyboard navigation is disabled if minDate or maxDate are null

[KevinFabre-ods]

Describe the bug
If minDate or maxDate have a value of null keyboard navigation thought days is disabled.

To Reproduce
Steps to reproduce the behavior:

render:

<ReactDatePicker 
   minDate={null} 
   maxDate={null}
/>

Expected behavior
Keyboard navigation should be enabled.

Desktop

Any OS or browser

Additional context
I ran into this issue because @types/react-datepicker defined type for minDate and maxDate as Date | null | undefined.
type for minTime and maxTime is Date | undefined.

I can make the edit on @types/react-datepicker, could you please confirm that the types for minDate and maxDate should be Date | undefined ?