I can Ignite Creepers With anything..

I was spawning mobs in the Nether, until I was spawning Creepers, I went near a Creeper holding a Spawn Egg, until I saw an 'Ignite' button. I went ahead and tapped it, only to let the Creeper explode..I tried to do the same thing in survival, but this time in the overworld, I went near a Creeper, and this time I was holding a dirt block, but an 'Ignite' button still appeared..
I hope you can understand this since this is my first bug report..and I don't know how to find any bug report relating to mine..