Fix: check if requirements exist on message

[1yam]

Problem: In some case (hold instance) there is no requirements field

Solutions: Add check if requirements field exist

[Psycojoker]

If possible, add a test on it

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 94.37%. Comparing base (9cb1456) to head (0441673). Report is 1 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #591 +/- ## ======================================= Coverage 94.37% 94.37% ======================================= Files 91 91 Lines 4909 4910 +1 Branches 677 677 ======================================= + Hits 4633 4634 +1 Misses 241 241 Partials 35 35 ```

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[1yam]

We already have a test that covers instance message processing without specific requirements, which is test_process_instance. You can find it here.

I have added a check for the node_hash field to ensure it aligns with the configuration of the instance. As the confidential one do