[C++] Allow pushing null value to vector (fixes #8424)

[shikharish]

Fixes #8424.

[shikharish]

@jtdavis777 Request for review.

[jtdavis777]

Hey! Thanks for the PR -- I think a test for this feature would be useful.

[shikharish]

I ran scripts/clang-format-all.sh and it formats many unchanged files. Should I submit those formatting changes in this PR itself?

[jtdavis777]

Things must be getting out of sync -- I 'm also dimly aware of the fact that clang-format may have some style preference differences between versions, so you may be encountering that. I would not stress it for this PR if you can manually ensure you're reasonably within the style, and we can submit a separate catch-up PR if needed.

[shikharish]

Alright, I'll submit another PR after this one gets merged.

[jtdavis777]

this one LGTM - I believe @dbaileychess is working on the repo right now and so merging is paused for a little while but I'll make sure this gets in once that is complete.

[jtdavis777]

@shikharish there is a bazel test compilation failure - can you take a look?

[aardappel]

Sorry this should not be merged, see my comment on the original issue.