SPIGOT-4916: Fix loading legacy structure data

nms-patches/IChunkLoader.patch

@@ -1,6 +1,6 @@
 --- a/net/minecraft/server/IChunkLoader.java
 +++ b/net/minecraft/server/IChunkLoader.java
-@@ -17,10 +17,51 @@
+@@ -17,15 +17,56 @@
          this.b = datafixer;
      }
  
@@ -53,3 +53,9 @@
          if (i < 1493) {
              nbttagcompound = GameProfileSerializer.a(this.b, DataFixTypes.CHUNK, nbttagcompound, i, 1493);
              if (nbttagcompound.getCompound("Level").getBoolean("hasLegacyStructureData")) {
+                 if (this.a == null) {
+-                    this.a = PersistentStructureLegacy.a(dimensionmanager, (WorldPersistentData) supplier.get());
++                    this.a = PersistentStructureLegacy.a(dimensionmanager.getType(), (WorldPersistentData) supplier.get()); // CraftBukkit - getType
+                 }
+ 
+                 nbttagcompound = this.a.a(nbttagcompound);