Fix null ref in UrlGroup.Dispose due to logger not set

[NGloreous]

Summary of the changes (Less than 80 chars)

• Fixing HttpSysRequestDelegationFeature - DelegationRule throws NullReferenceException on Dispose #26982 by passing the logger through to the new version of the UrlGroup constructor used by the HttpSysRequestDelegationFeature.
• Also fixing a null ref case I hit while calling DelegateRequest when passing a null DelegationRule, yes my bad but should probably do the check :)

[dnfadmin]

All CLA requirements met.

[shirhatti]

@NGloreous Can you please sign the CLA?

[Tratcher]

And re-target to the master branch please? I don't expect this to get approved for 5.0 at this point. We might be able to backport it for servicing later.

[NGloreous]

@shirhatti CLA signed.

@Tratcher updated to point to master. I wasn't quite sure what the process was to get this patched for 5.

[pranavkm]

Nullability should do a better job of validating this. Could we remove this check given that it's a non-public API?

[NGloreous]

@pranavkm HttpSys.FeatureContext.DelegateRequest which is public calls this method directly. I could move this check over there but figured it made more sense here since this is where it's used.

I don't quite get your point about nullability.

[shirhatti]

I wasn't quite sure what the process was to get this patched for 5.

It's too late to get this patched for 5. Given that there's an obvious workaround it won't meet the bar

[NGloreous]

@shirhatti what's the work around? If there are any issues in Dispose they will result in a null ref and no ability to have insight into the actual error.

[shirhatti]

@NGloreous Can you rebase to fix the merge conflicts?

[NGloreous]

@NGloreous Can you rebase to fix the merge conflicts?

@shirhatti done.

[ghost]

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