Update directive.ts

[wivjek]

Solving a bug : selection of a date is not possible anymore after this process with an input field date :

• select a date
• remove the date by deleting with keyboard
• go outside the field (focus lost) => here we can see errors in logs (js error "cannot clone() on undefined value")
• return to the field trying to select a date with mouse => KO = not possible (... But user is not blocked, he can always type a new date and then selection with mouse works again...)