Placeholder overlaps first option when `showAllValues: true`

[hannalaakso]

Screenshot

Steps to replicate:

1. Set up a progressively-enhanced select with a null option and a non-null option (see below), defaultValue: '', placeholder: 'PH', showAllValues: true:

<select name="last-location" id="last-location">
    <option value=""></option>
    <option value="value">Abu Dhabi</option>
</select>

2. Click on the input. The placeholder text and the first option now overlap.

Expected behaviour:

Placeholder text should disappear when user clicks on the field.

Note: this only happens when showAllValues: true.

(Placeholders are generally not recommended so I think this might be lower priority)