diff --git a/Source/Editor/Content/Proxy/PrefabProxy.cs b/Source/Editor/Content/Proxy/PrefabProxy.cs
index 39d77f25c..276bc0d30 100644
--- a/Source/Editor/Content/Proxy/PrefabProxy.cs
+++ b/Source/Editor/Content/Proxy/PrefabProxy.cs
@@ -162,8 +162,7 @@ namespace FlaxEditor.Content
 
                 // Auto fit actor to camera
                 float targetSize = 30.0f;
-                BoundingBox bounds;
-                Editor.GetActorEditorBox(_preview.Instance, out bounds);
+                Editor.GetActorEditorBox(_preview.Instance, out var bounds);
                 float maxSize = Mathf.Max(0.001f, bounds.Size.MaxValue);
                 _preview.Instance.Scale = new Vector3(targetSize / maxSize);
                 _preview.Instance.Position = Vector3.Zero;
@@ -175,6 +174,7 @@ namespace FlaxEditor.Content
         /// <inheritdoc />
         public override void OnThumbnailDrawEnd(ThumbnailRequest request, ContainerControl guiRoot)
         {
+            _preview.RemoveChildren();
             _preview.Prefab = null;
             _preview.Parent = null;
         }
diff --git a/Source/Engine/UI/UICanvas.cpp b/Source/Engine/UI/UICanvas.cpp
index 67dbaaa5e..49d6ac420 100644
--- a/Source/Engine/UI/UICanvas.cpp
+++ b/Source/Engine/UI/UICanvas.cpp
@@ -17,13 +17,17 @@ MMethod* UICanvas_OnDisable = nullptr;
 MMethod* UICanvas_EndPlay = nullptr;
 
 #define UICANVAS_INVOKE(event) \
-	MonoObject* exception = nullptr; \
-	UICanvas_##event->Invoke(GetManagedInstance(), nullptr, &exception); \
-	if (exception) \
-	{ \
-		MException ex(exception); \
-		ex.Log(LogType::Error, TEXT("UICanvas::" #event)); \
-	}
+    auto instance = GetManagedInstance(); \
+    if (instance) \
+    { \
+	    MonoObject* exception = nullptr; \
+	    UICanvas_##event->Invoke(instance, nullptr, &exception); \
+	    if (exception) \
+	    { \
+		    MException ex(exception); \
+		    ex.Log(LogType::Error, TEXT("UICanvas::" #event)); \
+	    } \
+    }
 
 UICanvas::UICanvas(const SpawnParams& params)
     : Actor(params)