Added null validation in RedirectHandler (#28276)
Added null validation in RedirectHandler (#28276)

Summary of the changes 
 - Added null check to response.headers.location to prevent NullReferenceException in RedirectHandler class

Addresses #27035 

aspnet/AspNetCore,aspnet/AspNetCore,aspnet/AspNetCore,aspnet/AspNetCore,aspnet/AspNetCore,aspnet/AspNetCore,aspnet/AspNetCore,aspnet/AspNetCore,aspnet/AspNetCore