KScreenlocker tries to clear the clipboard on load. However, klipper
also (by default) automatically keeps the last relevant item in the
clipboard. Whilst both parts work correctly, Plasma as a whole does not.
This became a problem when we added the reveal password button as it is
a data leak.
Instead of clearing the clipboard this patch replaces it with a real
entry, but with a dummy mime value that is of no value to anyone,
especially a textfield.