Unlucky keypresses get ignored due to buggy bailout logic

[sophiebits]

If you have an editor containing

ABC
defghi

and replace "d" with "A", or "e" with "B", or "f" with "C" by selecting the character and typing the new one, nothing happens.

That's because this check mistakenly slices relative to the entire editor content but the indices it's using are relative to a particular block:

https://github.com/facebook/draft-js/blob/2d7ad181d60b97a87e2f6fff6557ae31c02a8749/src/component/handlers/edit/editOnBeforeInput.js#L120-L127