Optional end date with no value isn't validating correctly.

The message Notice: Undefined index: value2 in date_field_validate() (line 291 of ...\www\sites\all\modules\date\date.field.inc) happens (I think) any time you have a date with an optional end date and don't supply one. The logic handling this is wrong and needs to be fixed.

I'm seeing this when using translations, but it is probably a bigger issue.