[rprospero]

In the hypothetical, the aliens haven't been wiped out yet by the singularity. As I see it, that leaves two options.

1) The aliens never stumbled upon AI. Considering that they've mastered interstellar travel, then they're likely very far ahead of us technologically. If they haven't stumbled across it, it's pretty unlikely that we will either. It's like quarantining otters because we're worried that they'll accidentally make an anti-matter bomb.

2) The aliens developed the singularity, but defeated it. Perhaps the Gulgaflak theorem provides a logic bomb that stops singularities from occurring. Maybe they tamed the AI into a benevolent force. Whatever it is, they have a way of handling AIs that are, again, more advanced than what we can develop. We don't quarantine otter because our tools are WAY better than theirs.

3) The aliens figured out AI, but decided not to use it. A species wide decision was made to not develop the technology once they figured out exactly how to do it. Considering the short term, local benefits to someone for cheating and doing it anyway, it's essentially the prisoner's dilemma, multiplied by everyone on the entire planet times all the centuries between their discovery of AI and their discovery of life on Earth.