build-multiversion fails on PR from fork

[christophfroehlich]

Describe the bug

sphinx-check-page-multiversion.yml seems to fail if someone opens a PR with a branch from a fork

Building multi version documentation with API
Step 1: Creating temporary commits
./make_help_scripts/add_tmp_commits.py
error: pathspec 'patch-1' did not match any file(s) known to git
Traceback (most recent call last):
  File "/home/runner/work/control.ros.org/control.ros.org/./make_help_scripts/add_tmp_commits.py", line 76, in <module>
Using base_branch: patch-1
    add_sub_repositories_and_commit()
  File "/home/runner/work/control.ros.org/control.ros.org/./make_help_scripts/add_tmp_commits.py", line 42, in add_sub_repositories_and_commit
    subprocess.run(["git", "checkout", deploy_defines.base_branch], check=True)
  File "/opt/hostedtoolcache/Python/3.10.16/x64/lib/python3.10/subprocess.py", line 526, in run
    raise CalledProcessError(retcode, process.args,
subprocess.CalledProcessError: Command '['git', 'checkout', 'patch-1']' returned non-zero exit status 1.
make: *** [Makefile:100: multiversion-with-api] Error 1

To Reproduce
https://github.com/ros-controls/control.ros.org/actions/runs/14204076690/job/39797555400