When growing the cactus doesn't break if there is a block next to it

What I expected to happen was...:
I thought the cactus would break because there is a block next to it.

What actually happened was...:
The cactus didn't break and there was a block next to it.

Steps to Reproduce:
1. Plant a cactus
2. Put a block next to where the cactus will grow.
3. Wait until it grow
4. You will see that the cactus isn't breaking.