re-add LevelTicks mixin for MC 1.21.4+

fabric/src/main/java/com/seibel/distanthorizons/fabric/mixins/server/MixinLevelTicks.java

@@ -0,0 +1,48 @@
+package com.seibel.distanthorizons.fabric.mixins.server;
+
+#if MC_VER < MC_1_21_4
+
+import net.minecraft.world.entity.Entity;
+import org.spongepowered.asm.mixin.Mixin;
+
+@Mixin(Entity.class)
+public class MixinLevelTicks<T>
+{
+	// dummy mixin to make the loader happy
+}
+
+#else
+
+import com.seibel.distanthorizons.common.wrappers.DependencySetupDoneCheck;
+
+import net.minecraft.world.ticks.LevelTicks;
+import net.minecraft.world.ticks.ScheduledTick;
+
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Inject;
+import org.spongepowered.asm.mixin.injection.callback.CallbackInfo;
+
+@Mixin(LevelTicks.class) // available in 1.18.2+, but only needed in 1.21.4+
+public class MixinLevelTicks<T>
+{
+	// TODO put in a common location
+	private static boolean isWorldGenThread()
+	{ return DependencySetupDoneCheck.isDone && DependencySetupDoneCheck.getIsCurrentThreadDistantGeneratorThread.get(); }
+	
+	
+	
+	@Inject(method = "schedule", at = @At(value = "HEAD"), cancellable = true)
+	private void onChunkSave(ScheduledTick<T> tick, CallbackInfo ci)
+	{
+		// In MC 1.21.4 an error check was added to log attempting to schedule ticks for unloaded chunks
+		// this caused a lot of unnecessary errors when generating sand (FallingBlock.class).
+		if (isWorldGenThread())
+		{
+			ci.cancel();
+		}
+	}
+	
+}
+
+#endif

fabric/src/main/resources/DistantHorizons.fabric.mixins.json

@@ -8,7 +8,8 @@
     "server.MixinEntity",
     "server.MixinServerPlayer",
     "server.MixinTracingExecutor",
-    "server.MixinUtilBackgroundThread"
+    "server.MixinUtilBackgroundThread", 
+    "server.MixinLevelTicks"
   ],
   "client": [
     "client.MixinClientLevel",