Running the following code showes You that air block is not able to replace glowstone or other blocks. Is it correct or failer? 

 
player.onChat("napis", function () {
blocks.print(
"Ahoj",
Block.Glowstone,
positions.create(0,0,20),
CompassDirection.West
)
loops.pause(2000)
blocks.print(
"Ahoj",
Block.Air,
positions.create(0,0,20),
CompassDirection.West
)
})
 
Thank you.