When set camera.targetTexture = null,I get "Tiled GPU perf. warning" and Inverted image

[saoexit]

Hey guys!
Here is a problem that has bothered me for a long time。
If there is more than one camera in the scene，And set the main camera.targetTexture = null
I’ll get a warning that it won’t be cleared
“Tiled GPU perf. warning: RenderTexture color surface (1280x720) was not cleared/discarded. See TiledGPUPerformanceWarning.ColorSurface label in Profiler for info”
More strangely，At this time, the image in the main camera buffer is inverted

Does anyone know what’s going on?
How can I correctly set the targetTextureof the main camera empty?

My Unity version is 2018.4.35f1,Using the built-in rendering pipeline
In the attachment is the scene of reproducing the bug

7427879–909452–bugTargetTexture.unitypackage (709 Bytes)
7427879–909452–bugTargetTexture.unitypackage (709 Bytes)

[saoexit]

public class newTargetTexture : MonoBehaviour
{
public bool isNull = true;
private void OnEnable()
{
if(isNull)
{
Camera.main.targetTexture = null;
}
var rtBuffer = RenderTexture.GetTemporary(Screen.width, Screen.height, 24);
var commandBuffer = new CommandBuffer();
commandBuffer.Blit(BuiltinRenderTextureType.CameraTarget, rtBuffer);
Camera.main.AddCommandBuffer(CameraEvent.AfterImageEffects, commandBuffer);
GetComponent().texture = rtBuffer;
}

}
Here’s what this code does, nothing else
I just call Camera.main.targetTexture = null well get warning