Save yourself the trouble

- Don't initialize instancers if they have 0 instances
- Never shrink the index pool
- Actually process recently allocated meshes to avoid growing the list
  forever

common/src/backend/java/dev/engine_room/flywheel/backend/engine/DrawManager.java

@@ -58,8 +58,13 @@ public abstract class DrawManager<N extends AbstractInstancer<?>> {
 	public void flush(LightStorage lightStorage, EnvironmentStorage environmentStorage) {
 		// Thread safety: flush is called from the render thread after all visual updates have been made,
 		// so there are no:tm: threads we could be racing with.
-		for (var instancer : initializationQueue) {
-			initialize(instancer.key(), instancer.instancer());
+		for (var init : initializationQueue) {
+			var instancer = init.instancer();
+			if (instancer.instanceCount() > 0) {
+				initialize(init.key(), instancer);
+			} else {
+				instancers.remove(init.key());
+			}
 		}
 		initializationQueue.clear();
 	}

common/src/backend/java/dev/engine_room/flywheel/backend/engine/MeshPool.java

@@ -70,23 +70,17 @@ public class MeshPool {
 		if (anyToRemove) {
 			anyToRemove = false;
 			processDeletions();
+		}
 
-			// Might want to shrink the index pool if something was removed.
-			indexPool.reset();
-			for (PooledMesh mesh : meshList) {
-				indexPool.updateCount(mesh.mesh.indexSequence(), mesh.indexCount());
-			}
-		} else {
+		if (!recentlyAllocated.isEmpty()) {
 			// Otherwise, just update the index with the new counts.
 			for (PooledMesh mesh : recentlyAllocated) {
 				indexPool.updateCount(mesh.mesh.indexSequence(), mesh.indexCount());
 			}
+			indexPool.flush();
 			recentlyAllocated.clear();
 		}
 
-		// Always need to flush the index pool.
-		indexPool.flush();
-
 		uploadAll();
         dirty = false;
     }