We are indeed now caught in a causal paradox.
The Empire uses Black Rose, triggering the Eighth Umbral Calamity. G'raha goes back in time to undo the Eighth Umbral Calamity and succeeds. Therefore, Good Future G'raha has no need to do so and is unavailable in the new timeline, so him going back in the Good Future isn't a possibility in said Good Future, which means the Bad Future should still happen... which would lead to G'raha being sent back to the past and making the Good Future...
Time travel is wonky and confusin', y'all.