Gamerules that were not in the version prior to updating are automatically set to false.

This applies to updating Skyblock (1.4 world) to 1.8 or updating a 1.14.4 world to 19w36a. This causes problems like crops not growing from 1.4->1.8, or no fall damage or phantoms from 1.14->19w36a.

How to replicate:
1- Make a world in 1.14 with cheats enabled so you can /gamerule.
2- Update to 19w36a on that world.
3- Do /gamerule drowningDamage/fallDamage/fireDamage/doInsomnia.

What I expected:
The gamerule should be set to its default.

What happened:
The gamerule is set to false.