Frankfurt am Main
You treat it just like you would if you rolled an unhelpful die on your own turn. "Oh, well, the next one'll be better." Basically, if you roll a bunch of useless die for your AI opponent, consider yourself lucky.
There has been a rule change here - you reroll 'unusable' Dice for the AI once!
What unusable means has been discussed in other topics here, you should find them easily!
My question: If all the AI ships are on the home base, the only unusable dice are economy and diplomacy... Are these the only dice you rolled? ;-)