Task Completion without a due date

First of all, I would like to note that I'm impressed with your script and like the clean look. Now on to the 'bug'.

I noticed that when adding a new item, without filling in a Due Date, this all goes well. The 'bug' appears when clicking the completed button, which strikethroughs the text, but also adds a date in the format 0000-00-00 where I didn't expect that to appear (since no date was input)