[release/7.0] [TS Client] Fix CompletionMessage result when passing false or null

[github-actions[bot]]

Backport of #45169 to release/7.0

/cc @BrennanConroy

[TS Client] Fix CompletionMessage result when passing false or null

Description

Returning false or "" or 0 would result in an unexpected exception on the server which the user would need to handle, instead it should give the value to the user code.

Fixes #45168

Customer Impact

Customer reported issue. This has been a bug forever, but it hasn't surfaced until now because it's only likely to show up when sending false from the client side in a streaming method, which is very unusual. It's now a lot easier to return a false value due to the "Client results" feature introduced in 7.0, so we should fix the problem in a 7.0 patch.

Regression?

• [ ] Yes
• [x] No

Risk

• [ ] High
• [ ] Medium
• [x] Low

Small fix and well understood, just an oversight and missed test coverage which are now resolved.

Verification

• [ ] Manual (required)
• [x] Automated

Packaging changes reviewed?

• [ ] Yes
• [ ] No
• [x] N/A

[ghost]

Hi @github-actions[bot]. Please make sure you've updated the PR description to use the Shiproom Template. Also, make sure this PR is not marked as a draft and is ready-to-merge.

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[ghost]

Hi @github-actions[bot]. This PR was just approved to be included in the upcoming servicing release. Somebody from the @dotnet/aspnet-build team will get it merged when the branches are open. Until then, please make sure all the CI checks pass and the PR is reviewed.

[BrennanConroy]

Servicing approved over email. @dotnet/aspnet-build please merge 😃