CorsPolicyBuilder.GetNormalizedOrigin NullReferenceException

[chrispickford]

Making a call to CorsPolicyBuilder.WithOrigins with an array that contains a null string will cause a NullReferenceException to be thrown rather than throwing against the argument. This was noticed when a configuration file failed to read.

To Reproduce

app.UseCors(builder => builder.WithOrigins(null));

System.NullReferenceException: Object reference not set to an instance of an object.
   at Microsoft.AspNetCore.Cors.Infrastructure.CorsPolicyBuilder.GetNormalizedOrigin(String origin)
   at Microsoft.AspNetCore.Cors.Infrastructure.CorsPolicyBuilder.WithOrigins(String[] origins)
   at ###.Startup.<Configure>b__11_0(CorsPolicyBuilder builder) in ###\Startup.cs:line 95
   at Microsoft.AspNetCore.Builder.CorsMiddlewareExtensions.UseCors(IApplicationBuilder app, Action`1 configurePolicy)
   at ###.Startup.Configure(IApplicationBuilder app, IHostingEnvironment env) in ###\Startup.cs:line 94
   at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state)

It would be beneficial if an ArgumentNullException was thrown instead.

[mkArtakMSFT]

Thanks for reporting this and submitting the PR, @chrispickford.
We will review the PR and get back to you next week.

[pranavkm]

Resolved as part of #19831.