Exceptions are thrown continuously on removing DirectX12 Graphics APIs from the list.

Steps to repro:
1. Create a new HDRP Template Project.
2. Change Graphics APIs to DirectX12 > Restart.
3. Create a Cube game object.
4. Remove DirectX12 from the list > Restart the Editor.
5. In Save Scene pop up click on Cancel.

Actual Result:
Errors are thrown in the console.

Expected Result:
No errors in the console.

Reproducible in:
2020.1.0a17, 2019.3.0f4 (e5c8d37da131), 2019.2.0f1, 2019.1.0b6.

Working Fine in:
2019.1.0b5.

Tested on Package Version: 7.1.6, 7.1.1.

Environment:
Occurs Only on Windows.

Stack trace:
System.ArgumentException: Kernel 'KSampleCopy4_1_x_8' not found.
at (wrapper managed-to-native) UnityEngine.ComputeShader.FindKernel(UnityEngine.ComputeShader,string)
at UnityEngine.Rendering.GPUCopy..ctor (UnityEngine.ComputeShader shader) [0x0000d] in C:\Users\GS1799\Downloads\New Unity Project (16)\Library\PackageCache\com.unity.render-pipelines.high-definition@7.1.6\Runtime\Core\CoreResources\GPUCopy.cs:12
at UnityEngine.Rendering.HighDefinition.HDRenderPipeline..ctor (UnityEngine.Rendering.HighDefinition.HDRenderPipelineAsset asset, UnityEngine.Rendering.HighDefinition.HDRenderPipelineAsset defaultAsset) [0x0059a] in C:\Users\GS1799\Downloads\New Unity Project (16)\Library\PackageCache\com.unity.render-pipelines.high-definition@7.1.6\Runtime\RenderPipeline\HDRenderPipeline.cs:343
at UnityEngine.Rendering.HighDefinition.HDRenderPipelineAsset.CreatePipeline () [0x00000] in C:\Users\GS1799\Downloads\New Unity Project (16)\Library\PackageCache\com.unity.render-pipelines.high-definition@7.1.6\Runtime\RenderPipeline\HDRenderPipelineAsset.cs:27
at UnityEngine.Rendering.RenderPipelineAsset.InternalCreatePipeline () [0x00004] in <ceab36736467481097fa2b52575c39a1>:0
UnityEngine.GUIUtility:ProcessEvent(Int32, IntPtr)