PM UI: NullReferenceException when signature validation fails

[dtivel]

1. Create a new test certificate .\CreateTestCertificate.ps1 –AddAsTrustedRootAuthority.
2. Sign a package: NuGet.exe sign <PackageFilePath> -CertificatePath <PfxFilePath>.
3. Create a project.
4. Add a NuGet.config file to the solution with the following content:

<configuration>
    <config>
        <add key="signatureValidationMode" value="require" />
    </config>
</configuration>

5. Save, close, and reopen the solution.
6. Open NuGet PM UI.
7. Add a package source for the directory containing the package signed in step 2.
8. Attempt to install that package.

Result:

System.NullReferenceException: Object reference not set to an instance of an object.
at NuGet.PackageManagement.UI.dll!NuGet.PackageManagement.UI.NuGetUI.ProcessSignatureIssues(NuGet.Packaging.Signing.SignatureException ex)