Default media type used when 'null' is passed to StringContent #81506

[slovely]

This fixes issue #81506

[ghost]

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Issue Details

---

This fixes issue #81506

Author:	slovely
Assignees:	-
Labels:	area-System.Net.Http
Milestone:	-

[dnfadmin]

All CLA requirements met.

[antonfirsov]

/azp run runtime

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[slovely]

This seems to be failing due to:

Console log: 'System.Net.Http.Functional.Tests' from job 1608dd3d-afff-484f-9f63-9fe3a5f70161 workitem fc399c4d-4353-44b5-b123-b6e5d9a2f9b3 (windows.amd64.server2022.open.rt) executed on machine a009IRU running Windows-10-10.0.20348-SP0

C:\h\w\B7EF09B6\w\AD35097A\e>taskkill.exe /f /im corerun.exe 
ERROR: The process "corerun.exe" not found.

That is the library that I added a test to, so it's seems too much of a coincidence that it isn't running... but I don't know what I could have done to have broken it I'm afraid!

[wfurt]

My guess is that it hits #83110. Offending change was reverted so you can try to rebase from mainline @slovely. That is probably easiest, otherwise we can look at the code dump.

[slovely]

@dotnet-policy-service agree

[antonfirsov]

If we backport this, I think this is a sufficient minimal fix to unblock people facing the unintentional breaking change. We should revisit the unintentional nullability changes for .NET 8.0, opened #83423 to track that.

[antonfirsov]

/backport to release/7.0

[github-actions]

Started backporting to release/7.0: https://github.com/dotnet/runtime/actions/runs/4420644720

[karelz]

@saber-wang @kevinle-1 you upvoted the PR. Did you run into the same problem?
If you did, can you please comment on the original issue #81506? If there are more people hitting it, that would support the backport, otherwise it won't have enough weight to get backported (yet). Thanks!