Discovered while testing MCPE-180498.

Flow and guster banner patterns does not render correctly after entered a non-1.21 experiment world.

Steps to Reproduce:

1. Enable the "Update 1.21" experiment.
2. Apply the banner patterns mentioned above onto a banner.
3. Place the banner down.
4. Exit the world.
5. Enter a world without "Update 1.21" experiment enabled.
6. Exit the world.
7. Reenter the world with banner.

Observed Results:
Flow and guster banner patterns does not render correctly after entered a non-1.21 experiment world.

Expected Results:
Flow and guster banner patterns would render correctly after entered a non-1.21 experiment world.