fix a couple of bugs with importing without material instances

Source/Editor/Content/Import/ModelImportEntry.cs

@@ -437,6 +437,12 @@ namespace FlaxEditor.Content.Import
 
         internal void ToInternal(out InternalOptions options)
         {
+            Guid instanceToImportAsGuid = Guid.Empty;
+            if (InstanceToImportAs != null)
+            {
+                instanceToImportAsGuid = InstanceToImportAs.ID;
+            }
+
             options = new InternalOptions
             {
                 Type = Type,
@@ -472,7 +478,7 @@ namespace FlaxEditor.Content.Import
                 TriangleReduction = TriangleReduction,
                 ImportMaterials = (byte)(ImportMaterials ? 1 : 0),
                 ImportMaterialsAsInstances = (byte)(ImportMaterialsAsInstances ? 1 : 0),
-                InstanceToImportAs = InstanceToImportAs.ID,
+                InstanceToImportAs = instanceToImportAsGuid,
                 ImportTextures = (byte)(ImportTextures ? 1 : 0),
                 RestoreMaterialsOnReimport = (byte)(RestoreMaterialsOnReimport ? 1 : 0),
                 GenerateSDF = (byte)(GenerateSDF ? 1 : 0),
@@ -484,6 +490,16 @@ namespace FlaxEditor.Content.Import
 
         internal void FromInternal(ref InternalOptions options)
         {
+            Material instanceToImportAsMat = null;
+            if (options.InstanceToImportAs != Guid.Empty)
+            {
+                AssetInfo assetInfo;
+                if (FlaxEngine.Content.GetAssetInfo(options.InstanceToImportAs, out assetInfo))
+                {
+                    instanceToImportAsMat = FlaxEngine.Content.Load<Material>(options.InstanceToImportAs);
+                }
+            }
+
             Type = options.Type;
             CalculateNormals = options.CalculateNormals != 0;
             SmoothingNormalsAngle = options.SmoothingNormalsAngle;
@@ -516,7 +532,7 @@ namespace FlaxEditor.Content.Import
             TriangleReduction = options.TriangleReduction;
             ImportMaterials = options.ImportMaterials != 0;
             ImportMaterialsAsInstances = options.ImportMaterialsAsInstances != 0;
-            InstanceToImportAs = FlaxEngine.Content.Load<Material>(options.InstanceToImportAs);
+            InstanceToImportAs = instanceToImportAsMat;
             ImportTextures = options.ImportTextures != 0;
             RestoreMaterialsOnReimport = options.RestoreMaterialsOnReimport != 0;
             GenerateSDF = options.GenerateSDF != 0;

Source/Engine/Content/Content.cpp

@@ -30,6 +30,7 @@
 #if ENABLE_ASSETS_DISCOVERY
 #include "Engine/Core/Collections/HashSet.h"
 #endif
+#include <Engine/Debug/DebugLog.h>
 
 TimeSpan Content::AssetsUpdateInterval = TimeSpan::FromMilliseconds(500);
 TimeSpan Content::AssetsUnloadInterval = TimeSpan::FromSeconds(10);
@@ -1003,6 +1004,7 @@ Asset* Content::load(const Guid& id, const ScriptingTypeHandle& type, AssetInfo&
     if (!GetAssetInfo(id, assetInfo))
     {
         LOG(Warning, "Invalid or missing asset ({0}, {1}).", id.ToString(Guid::FormatType::N), type.ToString());
+        LOG(Warning, "{0}", DebugLog::GetStackTrace());
         return nullptr;
     }
 

Source/Engine/Tools/ModelTool/ModelTool.cpp

@@ -863,18 +863,19 @@ bool ModelTool::ImportModel(const String& path, ModelData& meshData, Options& op
         importedFileNames.Add(filename);
 #if COMPILE_WITH_ASSETS_IMPORTER
         auto assetPath = autoImportOutput / filename + ASSET_FILES_EXTENSION_WITH_DOT;
-        if (options.ImportMaterialsAsInstances) {
+        if (options.ImportMaterialsAsInstances)
-            LOG(Warning, "Adding material instance for {0}", assetPath);
+        {
-
             AssetsImportingManager::Create(AssetsImportingManager::CreateMaterialInstanceTag, assetPath, material.AssetID);
             MaterialInstance* materialInstance = (MaterialInstance*) LoadAsset(assetPath, MaterialInstance::TypeInitializer);
-            if (materialInstance->WaitForLoaded()) {
+            if (materialInstance->WaitForLoaded())
+            {
                 LOG(Error, "Failed to load material instance after creation. ({0})", assetPath);
                 return true;
             }
 
             MaterialBase* materialInstanceOf = (MaterialBase*) LoadAsset(options.InstanceToImportAs, MaterialBase::TypeInitializer);
-            if (materialInstanceOf->WaitForLoaded()) {
+            if (materialInstanceOf->WaitForLoaded())
+            {
                 LOG(Error, "Failed to load material to create an instance of. ({0})", options.InstanceToImportAs);
                 return true;
             }
@@ -882,7 +883,8 @@ bool ModelTool::ImportModel(const String& path, ModelData& meshData, Options& op
             materialInstance->SetBaseMaterial(materialInstanceOf);
             materialInstance->Save();
         }
-        else {
+        else
+        {
             CreateMaterial::Options materialOptions;
             materialOptions.Diffuse.Color = material.Diffuse.Color;
             if (material.Diffuse.TextureIndex != -1)