NRE When Package Metadata CatalogPage Leaf returns 404

[mukunku]

NuGet Product Used

dotnet.exe, NuGet.exe, NuGet SDK

Product Version

dotnet sdk 8 and almost all versions of NuGet

Worked before?

Issue was introduced in #3462

Impact

It's more difficult to complete my work

Repro Steps & Context

You need to simulate a catalog page list where at least one of the range url 404's.

Here is the JSON my NuGet repo returns:

{
    "@id": "https://my.nuget.repo/v3/registration3-gz-semver2/my.package/index.json",
    "@type": [
        "catalog:CatalogRoot",
        "PackageRegistration",
        "catalog:Permalink"
    ],
    "count": 2,
    "items": [
        {
            "@id": "https://my.nuget.repo/v3/registration3-gz-semver2/my.package/page/7.4.3388/2018.4.0-enh-workersinclien13.json",
            "@type": "catalog:CatalogPage",
            "count": 128,
            "lower": "7.4.3388",
            "upper": "2018.4.0-enh-workersinclien13"
        },
        {
            "@id": "https://my.nuget.repo/v3/registration3-gz-semver2/my.package/page/7.4.3150/7.4.3387.json",
            "@type": "catalog:CatalogPage",
            "count": 128,
            "lower": "7.4.3150",
            "upper": "7.4.3387"
        }
    ]
}

The first page url returns a valid list of versions in that range ✔️ However the second one 404's and the leaf page ends up being null in the code here: https://github.com/NuGet/NuGet.Client/blob/7ad6fcc9c56c960975c37b2416c7eae1d53ba3fd/src/NuGet.Core/NuGet.Protocol/Resources/PackageMetadataResourceV3.cs#L122-L124

And because the if check is checking the wrong variable I get a NRE.

Verbose Logs

The issue happens when running `dotnet tool restore` with the following `dotnet-tools.json`

{
  "version": 1,
  "isRoot": true,
  "tools": {
    "my.package": {
      "version": "9.1.7",
      "commands": [
        "dotnet-tool"
      ]
    }
  }
}


[NuGet Manager] [Info]   GET https://my.nuget.repo/v3/registration3-gz-semver2/my.package/index.json
[NuGet Manager] [Info]   OK https://my.nuget.repo/v3/registration3-gz-semver2/my.package/index.json 237ms
[NuGet Manager] [Info]   GET https://my.nuget.repo/v3/registration3-gz-semver2/my.package/page/7.4.3388/2018.4.0-enh-workersinclien13.json
[NuGet Manager] [Info]   OK https://my.nuget.repo/v3/registration3-gz-semver2/my.package/page/7.4.3388/2018.4.0-enh-workersinclien13.json 108ms
[NuGet Manager] [Info]   GET https://my.nuget.repo/v3/registration3-gz-semver2/my.package/page/7.4.3150/7.4.3387.json
[NuGet Manager] [Info]   NotFound https://my.nuget.repo/v3/registration3-gz-semver2/my.package/page/7.4.3150/7.4.3387.json 131ms
Unhandled exception: System.NullReferenceException: Object reference not set to an instance of an object.
   at NuGet.Protocol.PackageMetadataResourceV3.ProcessRegistrationPage(RegistrationPage registrationPage, List`1 results, VersionRange range, Boolean includePrerelease, Boolean includeUnlisted, MetadataReferenceCache metadataCache)
   at NuGet.Protocol.PackageMetadataResourceV3.GetMetadataAsync(String packageId, Boolean includePrerelease, Boolean includeUnlisted, VersionRange range, SourceCacheContext sourceCacheContext, ILogger log, CancellationToken token)
   at NuGet.Protocol.PackageMetadataResourceV3.GetMetadataAsync(String packageId, Boolean includePrerelease, Boolean includeUnlisted, SourceCacheContext sourceCacheContext, ILogger log, CancellationToken token)
   at Microsoft.DotNet.Cli.NuGetPackageDownloader.NuGetPackageDownloader.GetPackageMetadataAsync(PackageSource source, String packageIdentifier, Boolean includePrerelease, Boolean includeUnlisted, CancellationToken cancellationToken)
   at Microsoft.DotNet.Cli.NuGetPackageDownloader.NuGetPackageDownloader.GetPackageMetadataAsync(String packageIdentifier, NuGetVersion packageVersion, IEnumerable`1 sources, CancellationToken cancellationToken, Boolean includeUnlisted)
   at Microsoft.DotNet.Cli.NuGetPackageDownloader.NuGetPackageDownloader.GetPackageSourceAndVersion(PackageId packageId, NuGetVersion packageVersion, PackageSourceLocation packageSourceLocation, Boolean includePreview, Boolean includeUnlisted, PackageSourceMapping packageSourceMapping)
   at Microsoft.DotNet.Cli.NuGetPackageDownloader.NuGetPackageDownloader.DownloadPackageAsync(PackageId packageId, NuGetVersion packageVersion, PackageSourceLocation packageSourceLocation, Boolean includePreview, Boolean includeUnlisted, Nullable`1 downloadFolder, PackageSourceMapping packageSourceMapping)
   at Microsoft.DotNet.Cli.ToolPackage.ToolPackageDownloader.DownloadAndExtractPackage(PackageLocation packageLocation, PackageId packageId, INuGetPackageDownloader nugetPackageDownloader, String packagesRootPath, IToolPackageStore toolPackageStore, NuGetVersion packageVersion, PackageSourceLocation packageSourceLoca
tion, Boolean includeUnlisted)
   at Microsoft.DotNet.Cli.ToolPackage.ToolPackageDownloader.<>c__DisplayClass8_0.<InstallPackage>b__0()
   at Microsoft.DotNet.Cli.TransactionalAction.Run[T](Func`1 action, Action commit, Action rollback)
   at Microsoft.DotNet.Tools.Tool.Restore.ToolRestoreCommand.InstallPackages(ToolManifestPackage package, Nullable`1 configFile)
   at Microsoft.DotNet.Tools.Tool.Restore.ToolRestoreCommand.<>c__DisplayClass10_0.<Execute>b__0(ToolManifestPackage package)
   at System.Linq.Enumerable.SelectArrayIterator`2.ToArray()
   at System.Linq.Enumerable.ToArray[TSource](IEnumerable`1 source)
   at Microsoft.DotNet.Tools.Tool.Restore.ToolRestoreCommand.Execute()
   at System.CommandLine.Invocation.InvocationPipeline.Invoke(ParseResult parseResult)
   at Microsoft.DotNet.Cli.Program.ProcessArgs(String[] args, TimeSpan startupTime, ITelemetry telemetryClient)