Melon and pumpkin stems do not break when block below them is broken or trampled

Summary:
When you break or trample farmland below a melon or pumpkin stem, the stem does not break.

Steps to Reproduce:

1. Till dirt/grass into farmland
2. Place water next to the farmland
3. Plant a melon/pumpkin seed on the farmland
4. Break or trample the farmland

Observed Results:
The stem floats in the air/remains planted on the dirt.

Expected Results:
The stem should break and drop as an item.