Cannot unset due date and start date by blanking the date in the editor

When you enter a start date and/or a due date in the task editor, the only way to unset the date is to click on the "Clear" button of the calendar. Actually the text input should be checked also since it is clearly easier to blank it than to click on the "Clear" button.

Or at least the input should not be editable, and a direct clear button should sit next to the button calling the calendar, to provide hint at how to remove a specified date