Revert "Change permanentOverrides to ConcurrentHashMap"

This reverts commit a5b5733.

We require the ability to store null values in the map for now

Author: embeddedt

common/src/main/java/org/embeddedt/modernfix/dynamicresources/DynamicBakedModelProvider.java

@@ -2,6 +2,7 @@
 
 import com.google.common.collect.ImmutableSet;
 import com.mojang.math.Transformation;
+import it.unimi.dsi.fastutil.objects.Object2ObjectOpenHashMap;
 import net.minecraft.client.renderer.block.model.BakedQuad;
 import net.minecraft.client.renderer.block.model.ItemOverrides;
 import net.minecraft.client.renderer.block.model.ItemTransforms;
@@ -21,7 +22,6 @@
 import org.jetbrains.annotations.Nullable;
 
 import java.util.*;
-import java.util.concurrent.ConcurrentHashMap;
 import java.util.function.BiFunction;
 import java.util.stream.Collectors;
 
@@ -85,7 +85,7 @@ public ItemOverrides getOverrides() {
     public DynamicBakedModelProvider(ModelBakery bakery, Map<Triple<ResourceLocation, Transformation, Boolean>, BakedModel> cache) {
         this.bakery = bakery;
         this.bakedCache = cache;
-        this.permanentOverrides = new ConcurrentHashMap<>();
+        this.permanentOverrides = Collections.synchronizedMap(new Object2ObjectOpenHashMap<>());
         if(currentInstance == null)
             currentInstance = this;
     }
@@ -109,12 +109,12 @@ public boolean isEmpty() {
 
     @Override
     public boolean containsKey(Object o) {
-        return o != null && permanentOverrides.getOrDefault(o, SENTINEL) != null;
+        return permanentOverrides.getOrDefault(o, SENTINEL) != null;
     }
 
     @Override
     public boolean containsValue(Object o) {
-        return o != null && (permanentOverrides.containsValue(o) || bakedCache.containsValue(o));
+        return permanentOverrides.containsValue(o) || bakedCache.containsValue(o);
     }
 
     private static boolean isVanillaTopLevelModel(ResourceLocation location) {
@@ -164,9 +164,6 @@ public BakedModel get(Object o) {
 
     @Override
     public BakedModel put(ResourceLocation resourceLocation, BakedModel bakedModel) {
-        if(resourceLocation == null)
-            return null;
-
         BakedModel m = permanentOverrides.put(resourceLocation, bakedModel);
         if(m != null)
             return m;
@@ -176,9 +173,6 @@ public BakedModel put(ResourceLocation resourceLocation, BakedModel bakedModel)
 
     @Override
     public BakedModel remove(Object o) {
-        if(o == null)
-            return null;
-
         BakedModel m = permanentOverrides.remove(o);
         if(m != null)
             return m;