Pedant, but the pressure difference between 1 atmosphere and zero isn't all that great, so explosive decompression wouldn't happen even in the worst case scenario. Rapid yes, explosive no.
To be explosive you need something like the Byford Dolphin diving bell incident, which was 9 atmospheres to 1 in a fraction of a second.
I dunno how it is in the US, but in the UK cats are considered "free spirits" and therefore their owners can't be held accountable for the cat's actions.
Jon can breathe easy.