Fix UOE when using generateTree with pale oak

[Warriorrrr]

Fixes an UOE error when the consumer/predicate generateTree methods are used with the pale oak tree type. I'm not sure if there's something inherently wrong with implementing getLevel here, but otherwise it could be fixed by passing only the generator along to the PaleMossDecorator.

java.lang.UnsupportedOperationException: Not supported yet.
	at org.bukkit.craftbukkit.util.DummyGeneratorAccess.getLevel(DummyGeneratorAccess.java:58) ~[main/:?]
	at net.minecraft.world.level.levelgen.feature.treedecorators.PaleMossDecorator.lambda$place$6(PaleMossDecorator.java:61) ~[main/:?]
	at java.base/java.util.Optional.ifPresent(Optional.java:178) ~[?:?]
	at net.minecraft.world.level.levelgen.feature.treedecorators.PaleMossDecorator.place(PaleMossDecorator.java:59) ~[main/:?]
	at net.minecraft.world.level.levelgen.feature.TreeFeature.lambda$place$8(TreeFeature.java:155) ~[main/:?]
	at java.base/java.lang.Iterable.forEach(Iterable.java:75) ~[?:?]
	at net.minecraft.world.level.levelgen.feature.TreeFeature.place(TreeFeature.java:155) ~[main/:?]
	at net.minecraft.world.level.levelgen.feature.Feature.place(Feature.java:192) ~[main/:?]
	at net.minecraft.world.level.levelgen.feature.ConfiguredFeature.place(ConfiguredFeature.java:25) ~[main/:?]
	at org.bukkit.craftbukkit.CraftRegionAccessor.generateTree(CraftRegionAccessor.java:291) ~[main/:?]
	at org.bukkit.craftbukkit.CraftRegionAccessor.generateTree(CraftRegionAccessor.java:200) ~[main/:?]