Photogrammetry load failure causes crash in OnCesium3DTilesetLoadFailure

倾斜摄影加载失败，在OnCesium3DTilesetLoadFailure里面销毁承载Cesium3DTileset的GameObject时会崩溃。

崩溃信息大致如下：

Obtained 24 stack frames
0x00007ffb330cf4ba (CesiumForUnityNative-Runtime) DotNet_CesiumForUnity_CesiumBingMapsRasterOverlay_AddToTileset
0x000001e2cbdec89f (Mono JIT Code) (wrapper managed-to-native) CesiumForUnity.Cesium3DTileset:DotNet_CesiumForUnity_Cesium3DTileset_Update (intptr,CesiumForUnity.Cesium3DTileset/ImplementationHandle)
0x000001e2cbdec683 (Mono JIT Code) [Cesium3DTileset-generated.cs:467] CesiumForUnity.Cesium3DTileset:Update ()
0x000001e1c2e76648 (Mono JIT Code) (wrapper runtime-invoke) object:runtime_invoke_void__this__ (object,intptr,intptr,intptr)
0x00007ffb503ffe24 (mono-2.0-bdwgc) [mini-runtime.c:3445] mono_jit_runtime_invoke
0x00007ffb5033e764 (mono-2.0-bdwgc) [object.c:3066] do_runtime_invoke
0x00007ffb5033e8fc (mono-2.0-bdwgc) [object.c:3113] mono_runtime_invoke
0x00007ff6cf784d44 (Unity) scripting_method_invoke
0x00007ff6cf7645e4 (Unity) ScriptingInvocation::Invoke
0x00007ff6cf74d8c4 (Unity) MonoBehaviour::CallMethodIfAvailable
0x00007ff6cf74d9b2 (Unity) MonoBehaviour::CallUpdateMethod
0x00007ff6cf23ad78 (Unity) BaseBehaviourManager::CommonUpdate
0x00007ff6cf24235a (Unity) BehaviourManager::Update
0x00007ff6cf45651d (Unity) `InitPlayerLoopCallbacks'::`2'::UpdateScriptRunBehaviourUpdateRegistrator::Forward
0x00007ff6cf43c70a (Unity) ExecutePlayerLoop
0x00007ff6cf43c896 (Unity) ExecutePlayerLoop
0x00007ff6cf442999 (Unity) PlayerLoop
0x00007ff6d03a25e9 (Unity) PlayerLoopController::UpdateScene
0x00007ff6d03a07ef (Unity) Application::TickTimer
0x00007ff6d07f0f5a (Unity) MainMessageLoop
0x00007ff6d07f580b (Unity) WinMain
0x00007ff6d1bb369e (Unity) __scrt_common_main_seh
0x00007ffbd96c26bd (KERNEL32) BaseThreadInitThunk
0x00007ffbdb26dfb8 (ntdll) RtlUserThreadStart