Previously, if the top match for "Smi" was "John Smith", the contents of
the field would be changed to "Smi[n Smith]" (where square brackets
indicate selection). On top of this, if you then type the fourth letter
("n"), the input becomes "Smin", which is not what you typed.
This preserves the "happy path" for replacing the field contents if
there is a prefix match, but without making the field unusable if
there's an infix match.