[backend] Validate contracts undefined, null or empty (#1121)

[savacano28]

Proposed changes

• Validate when contracts maps is null, empty or undefined

Related issues

• https://github.com/OpenBAS-Platform/openbas/issues/1121

Checklist

• [x] I consider the submitted work as finished
• [ ] I tested the code for its functionality
• [ ] I wrote test cases for the relevant uses case
• [ ] I added/update the relevant documentation (either on github or on notion)
• [x] Where necessary I refactored code to improve the overall quality

Further comments

If this is a relatively large or complex change, kick off the discussion by explaining why you chose the solution you did and what alternatives you considered, etc...

[codecov[bot]]

Codecov Report

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

Project coverage is 26.17%. Comparing base (6f6f545) to head (0a15268).

:exclamation: Current head 0a15268 differs from pull request most recent head 824abe3

Please upload reports for the commit 824abe3 to get more accurate results.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #1156 +/- ## ============================================ + Coverage 25.90% 26.17% +0.27% - Complexity 1062 1066 +4 ============================================ Files 481 481 Lines 11602 11602 Branches 609 609 ============================================ + Hits 3005 3037 +32 + Misses 8512 8480 -32 Partials 85 85 ```

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