Fix item loading in 1.13.2->1.13, 1.13->1.12

common/src/main/java/com/viaversion/viabackwards/api/data/BackwardsMappings.java

@@ -89,7 +89,7 @@ public class BackwardsMappings extends MappingDataBase {
         if (key.equals("items") && vvProtocolClass != null) {
             final MappingData mappingData = Via.getManager().getProtocolManager().getProtocol(vvProtocolClass).getMappingData();
             if (mappingData != null && mappingData.getItemMappings() != null) {
-                this.itemMappings = mappingData.getItemMappings().inverse();
+                return mappingData.getItemMappings().inverse();
             }
         }
         return super.loadBiMappings(data, key);

common/src/main/java/com/viaversion/viabackwards/protocol/protocol1_12_2to1_13/data/BackwardsMappings.java

@@ -32,7 +32,6 @@ import org.checkerframework.checker.nullness.qual.Nullable;
 public class BackwardsMappings extends com.viaversion.viabackwards.api.data.BackwardsMappings {
     private final Int2ObjectMap<String> statisticMappings = new Int2ObjectOpenHashMap<>();
     private final Map<String, String> translateMappings = new HashMap<>();
-    private BiMappings itemMappings;
 
     public BackwardsMappings() {
         super("1.13", "1.12", Protocol1_13To1_12_2.class);
@@ -42,7 +41,7 @@ public class BackwardsMappings extends com.viaversion.viabackwards.api.data.Back
     public void loadExtras(final CompoundTag data) {
         final Mappings itemsToMapped = loadMappings(data, "items");
         final BiMappings itemsToUnmapped = Protocol1_13To1_12_2.MAPPINGS.getItemMappings();
-        itemMappings = new BiMappings() {
+        this.itemMappings = new BiMappings() {
             @Override
             public BiMappings inverse() {
                 return itemsToUnmapped;