Add check for post existence in admin bar

[GautamMKGarg]

Patch for https://core.trac.wordpress.org/ticket/65128

Trac ticket: https://core.trac.wordpress.org/ticket/65128

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This Pull Request is for code review only. Please keep all other discussion in the Trac ticket. Do not merge this Pull Request. See GitHub Pull Requests for Code Review in the Core Handbook for more details.

[github-actions]

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Props gautammkgarg, apermo.

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[github-actions]

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[apermo]

LGTM, I also checked if any of the conditions might be cheaper for optimization, but the chosen order is already optimal.

[GautamMKGarg]

thanks @apermo for approving the code.

What is the next step? Do I need to do anything or the code with be merged automatically?

[apermo]

A core committer will have a final review and either point out something they find or merge.
so just wait