When gravel/sand disapearred when falling into plants

Put the summary of the bug you're having here

What I expected to happen was...:
When i was falling a sand or a gravel into a trapdoor when closed...

What actually happened was...:
The gravel or sand is disappear

Steps to Reproduce:
1. Build a trapdoor and its closed
2. Put a gravel or a sand on it
3. The gravel or sand was dissapearing