2 wide trees don't grow when next to dispenser.

When 2 wide trees are grown using dispensers nothing happens.

STEPS TO REPRODUCE:

-plant a 2 by 2 tree using spruce saplings.(don't grow it yet)

-place a dispenser next to the saplings pointing towards them and fill it with bonemeal.

-activate the dispenser via redstone clock.

Note that when the player uses bonemea on the saplings, it grows, however it does not when grown with the dispenser.

Please fix this bug, it makes automatic tree farms next to impossible.