Player can fall through scaffolding when sneaking if there is a collisionless block beneath the scaffolding

How to re-create bug:

Step 1: Set up a test site as the picture attached in this post.
Step 2: Sneak while on scaffolding of which beneath them has a non-full block (Torches. Item frame, Banner, etc.)

Expected result: 

Players should not be allowed to sneak and fall off scaffolding that doesn't have solid block beneath them.