SPIGOT-7966: Some trees do not generate with #generateTree

By: md_5 <git@md-5.net>

paper-server/src/main/java/org/bukkit/craftbukkit/util/BlockStateListPopulator.java

@@ -10,6 +10,7 @@ import java.util.function.Predicate;
 import net.minecraft.core.BlockPosition;
 import net.minecraft.core.IRegistryCustom;
 import net.minecraft.server.level.WorldServer;
+import net.minecraft.util.RandomSource;
 import net.minecraft.world.level.GeneratorAccess;
 import net.minecraft.world.level.block.ITileEntity;
 import net.minecraft.world.level.block.entity.TileEntity;
@@ -153,4 +154,10 @@ public class BlockStateListPopulator extends DummyGeneratorAccess {
     public long nextSubTickCount() {
         return world.nextSubTickCount();
     }
+
+    // SPIGOT-7966: Needed for some tree generations
+    @Override
+    public RandomSource getRandom() {
+        return world.getRandom();
+    }
 }