Fix null ref in DefaultControllerFactory

[Eilon]

See original code in https://aspnetwebstack.codeplex.com/SourceControl/network/forks/Therzok/fixNRERegression/contribution/5358

<! RouteData routeData = requestContext.RouteData;   
!> RouteData routeData = requestContext != null ? requestContext.RouteData : null;  

[dougbu]

NRE fixed in the original PR is no longer an issue because the method (GetControllerType(...)) now throws an ArgumentNullException a few lines earlier when requestContext == null.

On the other hand, DefaultControllerFactory lacks a null check for the RequestContext parameter in GetControllerInstance(...) and CreateController(...) and GetControllerType(...) both mishandle requestContext.RouteData. I'll send out a PR to address those small issues.

[dougbu]

3482799