No system shield for you

[Droplede]

So, in a solo game, my home system had a System Gravitational Shield Facility on a functional and happy planet. A few turns later, I had just built my first black-hole creator ship and, being contrary by nature, thought it would be fun to see if the shield actually stopped it. Saved the game, sent it to my home star and ... BAMF. No more home system, despite the Shield Facility. Did a triple-take, reloaded the save game, and successfully reproduced the destruction.

What gives? Anybody else ever see a case where the facility didn't work -- or DID work, for that matter? I'm a bit troubled by this.