Lava prevents beacons from activating.

To reproduce:

1. Create a new flat world in creative
2. Build a 3x3 beacon base using iron blocks
3. Place a beacon in the middle of the base
4. Observe that the beacon activates with the beacon beam going to the sky
5. Place lava on to of the beacon
6. Observe the the beacon deactivates.

Observed results:

Lava prevents a beacon from activating or deactivates beacon if placed on top of it.

Expected results:

Lava does not prevent beacon from activating.