[backend] fix null pointer exc

[savacano28]

Proposed changes

Related issues

Checklist

• [ ] 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

Attention: Patch coverage is 0% with 4 lines in your changes missing coverage. Please review.

Project coverage is 26.66%. Comparing base (0b9ca6a) to head (6068797).

Files	Patch %	Lines
...rc/main/java/io/openbas/service/InjectService.java	0.00%	4 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #1144 +/- ## ============================================ - Coverage 26.67% 26.66% -0.01% Complexity 1067 1067 ============================================ Files 474 474 Lines 11323 11325 +2 Branches 579 579 ============================================ Hits 3020 3020 - Misses 8219 8221 +2 Partials 84 84 ```

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