Can load but cannot unload resource packs.

Easy to recreate.

1. Go to resource packs menu. 2. Enable a resource pack. 3. Try to remove the resource pack. Don't even need to clock the done button it will not leave the enabled list.

Best way to unload the resource pack in 19w13a is to close the game completely and remove the resource pack you want to unload from the resource pack folder. Then load minecraft. Do not forget to place your resource pack back in resource packs folder.