Potions are not upgraded from damage values if there is no NBT tag.

Steps to Reproduce:

1. Open the attached world in 1.2.5
2. Observe the potions
3. Open it in 1.21.3
4. Observe the water bottles

Observed Results:

Opening the world in the latest version gives only water bottles.

Expected Behavior:

Opening the world in the latest version would give the original potions.

Code Analysis:

In ItemPotionFix, upgrading is only preformed if the OpticFinder for tag returned a present Optional, but potions from older versions may be missing the tag element.