When you try to empty a date or datetime field, you get a traceback saying that 'clone' and 'isSame' are not functions. This error occurs when you empty the field because the value is 'false' and you cannot call 'clone' or 'isSame' on false. To fix this, we ensure that value is not false before calling these methods on it. This bug has been introduced in rev: https://github.com/odoo/odoo/commit/c32724eae06c987e74a0600f1669696e499edc33