What is the effect of the follower's invalidation on the Imam's prayer when the follower is the sole person praying behind the Imam?

Primary text

When a follower invalidates their prayer while being the only one praying behind the Imam, the Imam's prayer is judged valid or invalid based on the principle of reciprocity in congregation. Since the validity of the follower's prayer is tied to the Imam's, the failure of the follower's prayer due to an invalidating act results in the same ruling applying to the follower as if the Imam had done it, given the established linkage between their prayers.