fix null check to unblock sdk

[kasperk81]

dotnet/sdk#41616
regression #102152

      EFCore.Benchmarks -> /vmr/src/efcore/artifacts/bin/EFCore.Benchmarks/Release/net8.0/EFCore.Benchmarks.dll
    /vmr/src/efcore/artifacts/sb/package-cache/microsoft.extensions.hostfactoryresolver.sources/9.0.0-preview.6.24315.2/contentFiles/cs/netstandard2.0/HostFactoryResolver.cs(166,28): error CS8619: Nullability of reference types in value of type 'string?[]' doesn't match target type 'string[]'. [/vmr/src/efcore/src/EFCore.Design/EFCore.Design.csproj]
##[error]/vmr/src/efcore/artifacts/sb/package-cache/microsoft.extensions.hostfactoryresolver.sources/9.0.0-preview.6.24315.2/contentFiles/cs/netstandard2.0/HostFactoryResolver.cs(166,28): error CS8619: (NETCORE_ENGINEERING_TELEMETRY=Build) Nullability of reference types in value of type 'string?[]' doesn't match target type 'string[]'.
      EFCore.SqlServer.Benchmarks -> /vmr/src/efcore/artifacts/bin/EFCore.SqlServer.Benchmarks/Release/net8.0/EFCore.SqlServer.Benchmarks.dll
  

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[buyaa-n]

LGTM, thank you

[MichalStrehovsky]

/ba-g failures are all known and attributed by build analysis

[MichalStrehovsky]

Merging to unblock codeflow to SDK repo

[kasperk81]

ci run was a waste because this code doesn't even build #103553

[ericstj]

It does build in tests.