Card.throwIn() error

Hello,

I try to throwIn() a card, but I get the following error message:
`TypeError: Cannot read property 'childNodes' of null`

I want to create a "back" button like on Tinder, so on swipe left/right I save the current Card and when I click on
the back button I just call prevCard.throwIn(0,0)

Start at the Card.throwIn() entry point and reproduce the reported prevCard.throwIn(0,0) sequence after a swipe. Trace the null value behind the childNodes error, then verify that using throwIn() for the back-button flow no longer throws and add regression coverage where the repository's existing tests allow.

Written by the indexing model from the issue text.