Error message when container image can't be found during container publish is confusing

I was trying to find the right value to put in the `` property in the project to switch to using the Azure Linux base images and attempted it with what was apparently the wrong value a few times. The resultant error message is confusing given the actual issue:

```
C:\Program
Files\dotnet\sdk\10.0.103\Containers\build\Microsoft.NET.Build.Containers.targets(261,5): error CONTAINER1015: Unable to access the repository 'dotnet/aspnet' at tag '10.0-azurelinux-3.0' in the registry ''. Please confirm that this name and tag are present in the registry. []
```

The `in the registry ''` was particularly confusing. Once I put the right value in (`azurelinux3.0` incidentally) it all worked fine.