Feeling empty

- Log a warning and don't allocate any resources when an instancer is
  created with an empty model.
- Log stacktrace starting from the call to InstancerProvider#instancer.
- Revert switch to embeddium dep and comment why the rubidium dep is
  there.

src/main/java/com/jozufozu/flywheel/backend/engine/InstancerStorage.java

@@ -5,6 +5,7 @@ import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 
+import com.jozufozu.flywheel.Flywheel;
 import com.jozufozu.flywheel.api.event.RenderStage;
 import com.jozufozu.flywheel.api.instance.Instance;
 import com.jozufozu.flywheel.api.instance.InstanceType;
@@ -51,6 +52,8 @@ public abstract class InstancerStorage<N extends AbstractInstancer<?>> {
 				return (Instancer<I>) instancer;
 			}
 
+			maybeWarnEmptyModel(model);
+
 			// Create a new instancer and add it to the uninitialized list.
 			instancer = create(type);
 			instancers.put(key, instancer);
@@ -59,6 +62,23 @@ public abstract class InstancerStorage<N extends AbstractInstancer<?>> {
 		}
 	}
 
+	private static void maybeWarnEmptyModel(Model model) {
+		if (!model.meshes()
+				.isEmpty()) {
+			// All is good.
+			return;
+		}
+
+		StringBuilder builder = new StringBuilder();
+		builder.append("Creating an instancer for a model with no meshes! Stack trace:");
+		StackWalker.getInstance()
+				.walk(s -> s.skip(3)) // skip 3 to get back to the caller of InstancerProvider#instancer
+				.forEach(f -> builder.append("\n\t")
+						.append(f.toString()));
+
+		Flywheel.LOGGER.warn(builder.toString());
+	}
+
 	public void delete() {
 		instancers.clear();
 		uninitializedInstancers.clear();

src/main/java/com/jozufozu/flywheel/backend/engine/indirect/IndirectDrawManager.java

@@ -46,6 +46,12 @@ public class IndirectDrawManager extends InstancerStorage<IndirectInstancer<?>>
 	@SuppressWarnings("unchecked")
 	@Override
 	protected <I extends Instance> void add(InstancerKey<I> key, IndirectInstancer<?> instancer, Model model, RenderStage stage) {
+		if (model.meshes()
+				.isEmpty()) {
+			// Don't bother allocating resources for models with no meshes.
+			return;
+		}
+
 		var group = (IndirectCullingGroup<I>) cullingGroups.computeIfAbsent(key.type(), IndirectCullingGroup::new);
 		group.add((IndirectInstancer<I>) instancer, model, stage);
 	}

src/main/java/com/jozufozu/flywheel/backend/engine/instancing/InstancedDrawManager.java

@@ -65,6 +65,12 @@ public class InstancedDrawManager extends InstancerStorage<InstancedInstancer<?>
 
 	@Override
 	protected <I extends Instance> void add(InstancerKey<I> key, InstancedInstancer<?> instancer, Model model, RenderStage stage) {
+		if (model.meshes()
+				.isEmpty()) {
+			// Don't bother allocating resources for models with no meshes.
+			return;
+		}
+
 		instancer.init();
 
 		DrawSet drawSet = drawSets.computeIfAbsent(stage, DrawSet::new);

src/main/resources/META-INF/mods.toml

@@ -30,8 +30,10 @@ ordering = "NONE"
 side = "CLIENT"
 
 [[dependencies.flywheel]]
-modId = "embeddium"
+modId = "rubidium"
 mandatory = false
-versionRange = "${embeddium_version_range}"
+# This should be a "breaks" dependency.
+# There's a mixin crash with Rubidum < 0.7.0
+versionRange = "[0.7.0,)"
 ordering = "NONE"
 side = "CLIENT"