Teleport to another dimension and place blocks underneath once in new dimension if nothing there

So I have made an item that when you right click with it you get teleported to that same spot in a void dimension and when you use it again you are sent back to the overworld to the exact same coordinates that you were at in the other dimension. What I need help with is when you use the item and get sent to the void dimension, I want it to check and see if there is something there and if nothing (air) is there then place a 3x3 dirt block to stand on as to not fall in the void. I have been trying lots of different things, but nothing is working for me as I have a smooth ape brain, lol. Any ideas are greatly appreciated.