Once upon a time, in a land not so far way, a boy, ShaneBee, was wandering around a strange blocky land.
He pondered the idea of venturing deep down into one of the mysterious caves he has seen.
Iron shovel in one hand... cooked chicken in the other, he felt prepared, he felt excited, he felt ready.
The excited yet anxious boy walked over to a cave he saw at the base of a large oak tree.
With a quick, deep breath in and a big gulp, he made the jump.
PHEW... in the cave we go.
Slowly the scared boy crept forward, and found himself in this open, bare cavern.
It was getting dark... he forgot his touches. He looked up and felt the dirt above may be thin enough to break thru for some light.
With this iron shovel, he reached up and broke some of the dirt above his head.
Light broke thru, he was relieved, he could see.
BUT.... he was stunned and whispered to himself "All this dirt around that hole, how is it not falling?"
He was confused, he was intrigued, he felt safe... knowing that the dirt didn't fall down and crush him to death, he truly felt like the Minecraft gods were on his side. They saved his life. They gave him another chance.

Ok so for the serious part. I noticed when breaking blocks in caves, the dirt/grass/etc weren't falling. Then looking at the source code I noticed there was a check for AIR below, but not CAVE_AIR.

I will be doing a PR very shortly to rectify this issue.