Vines don't drop as items when their supporting vine is sheared

The Bug:

Vines don't drop as items when their supporting vine is sheared.

Steps to Reproduce:

1. Build the setup shown in the attachment below. setup.png
2. Break the vine that is attached to the diamond block using some shears.
3. Observe if the vines that were being supported by the vine you just broke dropped as items.
4. Take note as to whether or not vines drop as items when their supporting vine is sheared.

Observed Behavior:

Vines don't drop as items when their supporting vine is sheared.

Expected Behavior:

Vines would drop as items when their supporting vine is sheared.