Fix "Not a string" Map Conversion spam - Fixes #3901

The maps did convert successfully, but had noisy logs due to Spigot
implementing this logic incorrectly.

This stops the spam by converting the old format to new before
requesting the world.

Spigot-Server-Patches/0583-Fix-Not-a-string-Map-Conversion-spam.patch

@@ -0,0 +1,43 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Aikar <aikar@aikar.co>
+Date: Thu, 8 Oct 2020 00:00:25 -0400
+Subject: [PATCH] Fix "Not a string" Map Conversion spam
+
+The maps did convert successfully, but had noisy logs due to Spigot
+implementing this logic incorrectly.
+
+This stops the spam by converting the old format to new before
+requesting the world.
+
+diff --git a/src/main/java/net/minecraft/server/WorldMap.java b/src/main/java/net/minecraft/server/WorldMap.java
+index 225353e072033d1e5aaf5604b8db255d9a154dc8..7ca4d279b9f13336ca425e413ff532f03bc0de0a 100644
+--- a/src/main/java/net/minecraft/server/WorldMap.java
++++ b/src/main/java/net/minecraft/server/WorldMap.java
+@@ -73,7 +73,26 @@ public class WorldMap extends PersistentBase {
+ 
+     @Override
+     public void a(NBTTagCompound nbttagcompound) {
+-        DataResult<ResourceKey<World>> dataresult = DimensionManager.a(new Dynamic(DynamicOpsNBT.a, nbttagcompound.get("dimension"))); // CraftBukkit - decompile error
++        // Paper start - fix "Not a string" spam
++        NBTBase dimension = nbttagcompound.get("dimension");
++        if (dimension instanceof NBTNumber && ((NBTNumber) dimension).asInt() >= CraftWorld.CUSTOM_DIMENSION_OFFSET) {
++            long least = nbttagcompound.getLong("UUIDLeast");
++            long most = nbttagcompound.getLong("UUIDMost");
++
++            if (least != 0L && most != 0L) {
++                this.uniqueId = new UUID(most, least);
++                CraftWorld world = (CraftWorld) server.getWorld(this.uniqueId);
++                if (world != null) {
++                    dimension = NBTTagString.create("minecaft:" + world.getName().toLowerCase(java.util.Locale.ENGLISH));
++                } else {
++                    dimension = NBTTagString.create("bukkit:_invalidworld_");
++                }
++            } else {
++                dimension = NBTTagString.create("bukkit:_invalidworld_");
++            }
++        }
++        DataResult<ResourceKey<World>> dataresult = DimensionManager.a(new Dynamic(DynamicOpsNBT.a, dimension)); // CraftBukkit - decompile error
++        // Paper end - fix "Not a string" spam
+         Logger logger = WorldMap.LOGGER;
+ 
+         logger.getClass();