Unity-Technologies/UnityCsReference · error · ArgumentNullException

Parameter asset is null

Error message

Parameter asset is null

What it means

Thrown by SpriteAtlasAsset.Save when the asset argument is null. Save serializes exactly one SpriteAtlasAsset via InternalEditorUtility.SaveToSerializedFileAndForget, which requires a real object; a null asset cannot be wrapped in the Object[] passed to the serializer. The exception type is ArgumentNullException with a combined paramName/message.

Source

Thrown at Editor/Mono/2D/SpriteAtlas/SpriteAtlasAsset.bindings.cs:182

        public void SetPackingSettings(SpriteAtlasPackingSettings src) { }
        [Obsolete("GetPackingSettings is no longer supported and will be removed. Use SpriteAtlasImporter.GetPackingSettings instead.")]
        public SpriteAtlasPackingSettings GetPackingSettings() { return new SpriteAtlasPackingSettings(); }
        [Obsolete("GetTextureSettings is no longer supported and will be removed. Use SpriteAtlasImporter.GetTextureSettings instead.")]
        public SpriteAtlasTextureSettings GetTextureSettings() { return new SpriteAtlasTextureSettings(); }
        [Obsolete("GetPlatformSettings is no longer supported and will be removed. Use SpriteAtlasImporter.GetPlatformSettingss instead.")]
        public TextureImporterPlatformSettings GetPlatformSettings(string buildTarget) { return new TextureImporterPlatformSettings(); }

        // Load SpriteAtlasAsset
        public static SpriteAtlasAsset Load(string assetPath)
        {
            var objs = UnityEditorInternal.InternalEditorUtility.LoadSerializedFileAndForget(assetPath);
            return (objs.Length > 0) ? objs[0] as SpriteAtlasAsset : null;
        }

        public static void Save(SpriteAtlasAsset asset, string assetPath)
        {
            if (asset == null)
                throw new ArgumentNullException("Parameter asset is null");
            var objs = new UnityEngine.Object[] { asset };
            UnityEditorInternal.InternalEditorUtility.SaveToSerializedFileAndForget(objs, assetPath, UnityEditor.EditorSettings.serializationMode != UnityEditor.SerializationMode.ForceBinary);
        }
    }
};

View on GitHub (pinned to 225b0fbdb5)

Solutions

1. Check the result of SpriteAtlasAsset.Load for null before Save.
2. Construct the SpriteAtlasAsset explicitly and confirm it is non-null before serializing.
3. Wrap migration loops with a null guard that logs the offending path and continues.
4. Validate assetPath exists with File.Exists before attempting Load+Save.

Example fix

// before
var asset = SpriteAtlasAsset.Load(srcPath);
SpriteAtlasAsset.Save(asset, dstPath);

// after
var asset = SpriteAtlasAsset.Load(srcPath);
if (asset == null) { Debug.LogError($"Failed to load atlas at {srcPath}"); return; }
SpriteAtlasAsset.Save(asset, dstPath);

if (asset == null) { Debug.LogError($"Cannot save: asset for {assetPath} is null (load failed?)."); return; }

When it happens

Trigger: Calling SpriteAtlasAsset.Save(null, path). Passing a SpriteAtlasAsset that failed to load (Load returned null) straight into Save. Creating a new asset via 'new SpriteAtlasAsset()' through an API that returned null on failure.

Common situations: Editor scripts that clone or migrate .spriteatlas files, where the source Load returned null (missing/corrupt file) but the script proceeded to Save. Batch conversion tooling that iterates many paths and does not check Load's null return.

Related errors

• Value for parameter atlases is null
• One of the elements in atlases is null. Please check your In
• gameObject
• bindings must be non-null
• keyframes must be non-null

AI-assisted analysis of Unity-Technologies/UnityCsReference@225b0fbdb5 (2026-08-13). Data as JSON: /api/errors/fdb9dc33db0c4a65. Report an issue: GitHub.