I would assume that this wouldn't be safe. While cycling ammonia levels and nitrite levels spike. Frogs absorb water through their skin so I can't imagine that would be a pleasant experience. I would suggest getting a bucket or something and putting your filter and extra media and some decorations in there and cycle it in there and then transfer that all to the water portion of your vivarium. The biological filter may need to adjust once being transferred but it will be much safer than going through a full cycle.