[backend] Fix Promote observable component crashes (#6399)

[SouadHadjiat]

Proposed changes

• handle case where observable.extensions[STIX_EXT_OCTI_SCO] is undefined

Related issues

• [Playbook] "Promote observable" component crashes #6399

To reproduce the issue, you need to create an observable (reproduced with ipv4) without description nor score. then follow the steps described in the issue.

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)
• Where necessary I refactored code to improve the overall quality

[codecov]

Codecov Report

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

Project coverage is 67.26%. Comparing base (1e90cee) to head (2d3ade3).

Files	Patch %	Lines
...raphql/src/modules/playbook/playbook-components.ts	0.00%	4 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #6402   +/-   ##
=======================================
  Coverage   67.26%   67.26%           
=======================================
  Files         541      541           
  Lines       65075    65075           
  Branches     5397     5398    +1     
=======================================
+ Hits        43770    43772    +2     
+ Misses      21305    21303    -2     

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[labo-flg]

Tested ok, but we need to rework the typescript and related stix converters. This can hide bugs.