Fixes chunks not loading PDC sometimes

If a chunk had no entities or block entities, it would fail
to load the PDC. This adds an additional check to see if there is
PDC and then to load that if so.

See: https://hub.spigotmc.org/jira/browse/SPIGOT-6814

patches/server/0811-Load-chunk-PDC-if-present.patch

@@ -0,0 +1,21 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Jake <jake.m.potrebic@gmail.com>
+Date: Sun, 28 Nov 2021 12:34:51 -0800
+Subject: [PATCH] Load chunk PDC if present
+
+
+diff --git a/src/main/java/net/minecraft/world/level/chunk/storage/ChunkSerializer.java b/src/main/java/net/minecraft/world/level/chunk/storage/ChunkSerializer.java
+index e072a895ed71bb2e98a3a0c4aef37418c7c39f41..c7f9e155b14beab5b0ba1d4debddc9747f13675d 100644
+--- a/src/main/java/net/minecraft/world/level/chunk/storage/ChunkSerializer.java
++++ b/src/main/java/net/minecraft/world/level/chunk/storage/ChunkSerializer.java
+@@ -687,8 +687,9 @@ public class ChunkSerializer {
+     private static LevelChunk.PostLoadProcessor postLoadChunk(ServerLevel world, CompoundTag nbt) {
+         ListTag nbttaglist = ChunkSerializer.getListOfCompoundsOrNull(nbt, "entities");
+         ListTag nbttaglist1 = ChunkSerializer.getListOfCompoundsOrNull(nbt, "block_entities");
++        boolean hasPdc = nbt.contains("ChunkBukkitValues", Tag.TAG_COMPOUND); // Paper
+ 
+-        return nbttaglist == null && nbttaglist1 == null ? null : (chunk) -> {
++        return nbttaglist == null && nbttaglist1 == null && !hasPdc ? null : (chunk) -> { // Paper
+             if (nbttaglist != null) {
+                 world.addLegacyChunkEntities(EntityType.loadEntitiesRecursive(nbttaglist, world));
+             }