Allow COW in StaticTagHelper

Seems that some mods bind tags at runtime. This is a hack but it
should fix the persistent CME I get when launching ATM6

src/main/java/org/embeddedt/modernfix/mixin/bugfix/concurrency/StaticTagHelperMixin.java

@@ -0,0 +1,28 @@
+package org.embeddedt.modernfix.mixin.bugfix.concurrency;
+
+import net.minecraft.tags.StaticTagHelper;
+import net.minecraft.tags.TagCollection;
+import net.minecraft.tags.TagContainer;
+import org.spongepowered.asm.mixin.Final;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.Mutable;
+import org.spongepowered.asm.mixin.Shadow;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Inject;
+import org.spongepowered.asm.mixin.injection.callback.CallbackInfo;
+
+import java.util.List;
+import java.util.concurrent.CopyOnWriteArrayList;
+import java.util.function.Function;
+
+@Mixin(StaticTagHelper.class)
+public class StaticTagHelperMixin<T> {
+    @SuppressWarnings("rawtypes")
+    @Shadow @Mutable
+    @Final private List wrappers;
+
+    @Inject(method = "<init>", at = @At("RETURN"))
+    private void useCOWArrayList(Function<TagContainer, TagCollection<T>> function, CallbackInfo ci) {
+        this.wrappers = new CopyOnWriteArrayList<>();
+    }
+}

src/main/resources/modernfix.mixins.json

@@ -55,6 +55,7 @@
     "perf.skip_first_datapack_reload.MinecraftMixin",
     "bugfix.concurrency.RenderTypeMixin",
     "bugfix.concurrency.MinecraftMixin",
+    "bugfix.concurrency.StaticTagHelperMixin",
     "perf.parallelize_model_loading.ModelBakeryMixin",
     "perf.parallelize_model_loading.OBJLoaderMixin",
     "perf.parallelize_model_loading.multipart.MultipartMixin",