Don't require parts to be unbroken for fake part generation

[irwiss]

Summary

None

Purpose of change

Fix #71451

Describe the solution

Fake parts require unbroken real parts for generating the fake part, when a part goes to XX the relative_parts cache is still populated with the mount point of the fake part, but the part is no longer there and causes a debugmsg in display code that uses the cache for lookup.

Could also repopulate the relative_parts when a part damage goes to XX, but imo fake parts should be generated regardless of broken status, and a hit to the same mount point should still apply damage and finish breaking off the XX part

Describe alternatives you've considered

Testing

Scenario in linked issue works for testing

Additional context

[ashGlaw]

Yass! I've run into this bug many times. Thank you for squashing it