I opened a world in 19w07a that I've been adding to using most of the 1.14 snapshots .  My well-lit and fenced village was overrun by mobs during the first 19w07a night, which kept the golums busy.  It turned out that none of the torches were affecting the block light level.  However, when I replaced a torch in 19w07a, the new torch had the expected light level. See attached screenshots.

What I expected to happen was...:
I expected 19w07a torch block light levels to be the same as they been in previous snapshots and releases.

What actually happened was...:
Torches placed in earlier snapshots had block light level of 0 when I opened the world in 19w07a.

Steps to Reproduce:
1. Create a world in a snapshot earlier than 19w07a
2. Place a torch and note the block light level
3. Open the world in 19w07a and note the torch block light level. I see 0.

4. Replace the torch in 19w07a and note the torch block light level. I see expected value, e.g.13 when standing 2 blocks away