The bug
Using bone meal on fern, grass or seagrass, which has not enough air / water above to turn into the tall variant, uses the bone meal anyways.
To reproduce
Place a block above a fern above a grass block
Attempt to apply bone meal to the fern
Observed behavior
The bone meal is consumed, even though the fern is unable to grow.
Expected behavior
The bone meal would not be consumed when the fern is unable to grow.
Affects 18w20a