dotnet.runtimeconfig.json is empty when docker build executed

### URL

https://dotnet.microsoft.com/en-us/learn/aspnet/microservice-tutorial/docker-image

### Operating system

Windows

### More information about your system

Windows 10 Pro 22H2
x64

### Description

Ran as provided by tutorial: docker build -t mymicroservice .
Got
=> ERROR [build 4/6] RUN dotnet restore
------
> [build 4/6] RUN dotnet restore:
0.446 A JSON parsing exception occurred in [/usr/share/dotnet/sdk/8.0.402/dotnet.runtimeconfig.json], offset 0 (line 1, column 1): The document is empty.
0.446 Invalid runtimeconfig.json [/usr/share/dotnet/sdk/8.0.402/dotnet.runtimeconfig.json] [/usr/share/dotnet/sdk/8.0.402/dotnet.runtimeconfig.dev.json]

exit code: 147

### dotnet --info

.NET SDK:
Version: 8.0.402
Commit: 70aa751718
Workload version: 8.0.400-manifests.251308be
MSBuild version: 17.11.4+37eb419ad

Runtime Environment:
OS Name: Windows
OS Version: 10.0.19045
OS Platform: Windows
RID: win-x64
Base Path: C:\Program Files\dotnet\sdk\8.0.402\

.NET workloads installed:
Configured to use loose manifests when installing new manifests.
There are no installed workloads to display.

Host:
Version: 8.0.8
Architecture: x64
Commit: 08338fcaa5

.NET SDKs installed:
8.0.400 [C:\Program Files\dotnet\sdk]
8.0.402 [C:\Program Files\dotnet\sdk]

.NET runtimes installed:
Microsoft.AspNetCore.App 8.0.8 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.NETCore.App 6.0.33 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 8.0.8 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.WindowsDesktop.App 6.0.33 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 8.0.8 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]

Other architectures found:
x86 [C:\Program Files (x86)\dotnet]
registered at [HKLM\SOFTWARE\dotnet\Setup\InstalledVersions\x86\InstallLocation]

Environment variables:
Not set

global.json file:
Not found