Encountered a bug while killing off the Cravers...

They had a tiny ground force remaining on one of my planets when I conquered their last system and now, because it thinks it is out of the game, the AI won't select a tactic allowing the battle to take place.

I'm also not able to end the turn due to the outstanding combat.

Workaround is to revert to an autosave to resolve that ground combat while the Cravers are still in the game before taking over their last system.