Checking for null for FileTrigger's onSelect() callback

[denchen]

For <FileTrigger>, the arguments for the callback onSelect() is typed as possibly being null

/**
  * Handler when a user selects a file.
  */
onSelect?: (files: FileList | null) => void,

Under what condition would this be null? A failed upload? No files selected? I ask because in your documentation, you don't check against null:

https://react-spectrum.adobe.com/react-aria/FileTrigger.html#example

function Example(){
  let [file, setFile] = React.useState(null);

  return (
    <>
      <FileTrigger
        onSelect={(e) => {
          let files = Array.from(e);
          let filenames = files.map((file) => file.name);
          setFile(filenames);
        }}>
        <Button>Select a file</Button>
      </FileTrigger>
      {file && file}
    </>
  )
}

[snowystinger]

The type for typescript input onChange always includes null, it doesn't know what type of event it is. I guess we could assert that it's never null for this one, as suggested in this discussion https://www.reddit.com/r/typescript/comments/19dqio6/what_is_the_correct_type_for_input_file_onchange/