Saplings obtained by pick-blocking leaves in version 1.2.5 are turned into incorrect types when upgrading the world

In version 1.2.5, pick-blocking leaves gave you a sapling of that type instead of leaves. However, when upgrading a world, saplings obtained this way do not upgrade correctly.

How to reproduce:

1. Start version 1.2.5
2. Place oak leavss
3. Use the pick block function on the oak leaves
4. Place spruce leaves
5. Use the pick block function on the spruce leaves
6. Place birch leaves
7. Use the pick block function on the birch leaves
8. Place jungle leaves
9. Use the pick block function on the jungle leaves
10. Open the world in the latest version

Expected result

Oak sapling would remain oak sapling, spruce sapling would remain spruce sapling, birch sapling would remain birch sapling, and jungle sapling would remain jungle sapling.

Observed result:

Oak sapling turns into acacia sapling, spruce sapling turns into dark oak sapling, birch sapling turns into oak sapling, and jungle sapling turns into oak sapling.