[Issue] Only deny customer access to order if it actually exists

[m2-assistant]

This issue is automatically created based on existing pull request: #38647: Only deny customer access to order if it actually exists

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Description (*)

This allows loading nonexistent orders by customer.
Before: loading an empty order as a customer would trigger this check resulting in "No such entity with orderId = ", as there is no orderId yet since it doesn't exist yet.
Which means the order should be allowed.

After: Loading an empty order results in the empty order being returned, if it is a preexisting order the old checks apply

Contribution checklist (*)

• Pull request has a meaningful description of its purpose
• All commits are accompanied by meaningful commit messages
• All new or changed code is covered with unit/integration tests (if applicable)
• README.md files for modified modules are updated and included in the pull request if any README.md predefined sections require an update
• All automated tests passed successfully (all builds are green)