When making Sethbling's cactus farm in 14w25b the vines would hold up the sand so it wouldn't fall and break the farm. When a cactus grows to the height of 2 the vine breaks and down falls all of the sand

To reproduce:
1.Make a module or two of Sethbling's Cactus Farm,
2. Wait for cactus to grow and vines break and then sand fall