fix code that generates console warnings and errors

Summary: As stated in our release guidelines, code "should not emit any warnings on the JavaScript console", yet we have lots of code that does. This includes:

• PropTypes errors due to bad isRequired statements. If you're seeing this warning, the prop is not, in fact, always present in the calling code.
• PropTypes errors that are just wrong. Often, an item is later replaced by a list, or an object by an array depending on which part of a resource is supplied i.e. the full resource (an object) or just its records (an array)).
• PropTypes errors due to bad shape. This is common for refs; the correct PropType is:

  PropTypes.oneOfType([
        PropTypes.func,
        PropTypes.shape({ current: PropTypes.instanceOf(Element) })
      ]),
  

• Memory leaks due to updating state in promises that finish executing after a component has unmounted:

  Warning: Can't perform a React state update on an unmounted component. 
  This is a no-op, but it indicates a memory leak in your application. To fix, 
  cancel all subscriptions and asynchronous tasks in a useEffect cleanup function.