Fix segfault when creating two participant with same fixed id [18051] (backport #3443)

[mergify]

This is an automatic backport of pull request #3443 done by Mergify.
Cherry-pick of 3a168ed has failed:

On branch mergify/bp/2.6.x/pr-3443
Your branch is up to date with 'origin/2.6.x'.

You are currently cherry-picking commit 3a168ed6f.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	modified:   src/cpp/fastdds/domain/DomainParticipantFactory.cpp
	modified:   test/mock/dds/DomainParticipantImpl/fastdds/domain/DomainParticipantImpl.hpp
	modified:   test/mock/rtps/RTPSDomainImpl/rtps/RTPSDomainImpl.hpp
	modified:   test/unittest/dds/participant/ParticipantTests.cpp

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   src/cpp/fastdds/domain/DomainParticipantImpl.cpp
	both modified:   src/cpp/rtps/RTPSDomain.cpp
	both modified:   src/cpp/rtps/RTPSDomainImpl.hpp

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/github/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

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