Clarify nature of missing modifier stack object references, AddModifierStack->AddModifierStacks

Runtime/Mapbox/VectorModule/IVectorLayerVisualizer.cs

@@ -12,7 +12,7 @@ namespace Mapbox.VectorModule
     public interface IVectorLayerVisualizer
     {
         string VectorLayerName { get; }
-        void AddModifierStack(List<ModifierStack> stack);
+        void AddModifierStacks(IEnumerable<ModifierStack> stacks);
         Dictionary<int, HashSet<MeshData>> CreateMesh(CanonicalTileId tileId, VectorTileLayer layer);
         List<GameObject> CreateGo(CanonicalTileId tileId, Dictionary<int, HashSet<MeshData>> meshData);
         void UnregisterTile(CanonicalTileId tileId);

Runtime/Mapbox/VectorModule/Unity/VectorLayerVisualizerObject.cs

@@ -32,7 +32,8 @@ public IVectorLayerVisualizer ConstructLayerVisualizer(IMapInformation mapInform
 			{
 				modifierStackObject.Initialize(unityContext);
 			}
-			_layerVisualizer.AddModifierStack(_modifierStackObjects.Select(x => x.GetModifierStack).ToList());
+			_layerVisualizer.AddModifierStacks(_modifierStackObjects.Select((x, i) => x?.GetModifierStack 
+				?? throw new NullReferenceException($"{name} ({nameof(VectorLayerVisualizerObject)}) is missing {nameof(ModifierStackObject)} reference @ element {i}")));
 
 			_layerVisualizer.OnVectorMeshCreated += OnVectorMeshCreated;
 			_layerVisualizer.OnVectorMeshDestroyed += OnVectorMeshDestroyed;

Runtime/Mapbox/VectorModule/VectorLayerVisualizer.cs

@@ -108,9 +108,9 @@ public IEnumerator Initialize()
             yield return null;
         }
 
-        public void AddModifierStack(List<ModifierStack> stack)
+        public void AddModifierStacks(IEnumerable<ModifierStack> stacks)
         {
-            foreach (var modifierStack in stack)
+            foreach (var modifierStack in stacks)
             {
                 _stackList.Add(modifierStack.GetHashCode(), modifierStack);
             }