[PreviewSystem] duplicated refreshes are triggered when loading the scene.

[Tliks]

起動時やPlayMode終了時に全フィルターのinstantiateが完了したタイミングで以下のエラーを挟み同一のフィルターのinstantiateが再度走ることで合計2回呼ばれているように見えます。

その後 #376 によりシーン上から選択すると再度instantiateが呼ばれるため、合計3回呼ばれているように見えます。

TTT AtlasTextureとこちらの実装の2つで確認しました。

NDMF: 1.5.0-rc.4

UnityException: get_gameObject can only be called from the main thread.
Constructors and field initializers will be executed from the loading thread when loading a scene.
Don't use this function in the constructor or field initializers, instead move initialization code to the Awake or Start function.
nadena.dev.ndmf.preview.NodeController.Create (nadena.dev.ndmf.preview.IRenderFilter filter, nadena.dev.ndmf.preview.RenderGroup group, nadena.dev.ndmf.ObjectRegistry registry, System.Collections.Generic.List`1[T] proxies, System.String trace) (at ./Packages/nadena.dev.ndmf/Editor/PreviewSystem/Rendering/NodeController.cs:107)
nadena.dev.ndmf.preview.ProxyPipeline+<>c__DisplayClass22_2.<Build>b__4 (System.Threading.Tasks.Task`1[TResult] items) (at ./Packages/nadena.dev.ndmf/Editor/PreviewSystem/Rendering/ProxyPipeline.cs:231)
nadena.dev.ndmf.preview.ProxyPipeline.Build (nadena.dev.ndmf.preview.ProxyObjectCache proxyCache, System.Collections.Generic.IEnumerable`1[T] filters, nadena.dev.ndmf.preview.ProxyPipeline priorPipeline) (at ./Packages/nadena.dev.ndmf/Editor/PreviewSystem/Rendering/ProxyPipeline.cs:263)
Rethrow as AggregateException: One or more errors occurred. (get_gameObject can only be called from the main thread.
Constructors and field initializers will be executed from the loading thread when loading a scene.
Don't use this function in the constructor or field initializers, instead move initialization code to the Awake or Start function.)
UnityEngine.Debug:LogException(Exception)
nadena.dev.ndmf.preview.ProxyPipeline:ShowError() (at ./Packages/nadena.dev.ndmf/Editor/PreviewSystem/Rendering/ProxyPipeline.cs:341)
nadena.dev.ndmf.preview.ProxySession:OnPreCull(Boolean) (at ./Packages/nadena.dev.ndmf/Editor/PreviewSystem/Rendering/ProxySession.cs:82)
nadena.dev.ndmf.preview.PreviewSession:OnPreCull(Boolean) (at ./Packages/nadena.dev.ndmf/Editor/PreviewSystem/PreviewSession.cs:51)
nadena.dev.ndmf.preview.ProxyManager:OnPreCull(Camera) (at ./Packages/nadena.dev.ndmf/Editor/PreviewSystem/ProxyManager.cs:61)
UnityEngine.GUIUtility:ProcessEvent(Int32, IntPtr, Boolean&)