Diffing two strings sometimes adds a blank change  #2

Diffing two strings sometimes adds a blank change

Sometimes when I diff two strings, the resulting array has a blank change.
For example:

Diff::LCS.diff 'hi', 'hie'

returns a two-element array where the first is a Diff::LCS::Change with @element="". I don't know why that
is there at all.

Diff::LCS.diff 'hi', 'hi'

should return an empty array but instead returns an array with the blank change (@element = "").

This does not always happen, as in the case with:

Diff::LCS.diff 'hie', 'hi'

correctly returns a one-element array.