upload for new PR when parent is merged is not handled gracefully

[juanique]

master@d4f6fa9b (Remote) https://github.com/juanique/monorepo/commit/d4f6fa9b: a day ago - Fix an issue that was causing submodules
├── add_support_for_gaze_89350 ↟ https://github.com/juanique/monorepo/pull/96: Add support for gazelle-python
├── copy_file_rule_3185e ↟ https://github.com/juanique/monorepo/pull/105: copy_file_rule
├── dont_rebase/upload_c_2f8ff https://github.com/juanique/monorepo/pull/111: Dont rebase/upload commits that dont nee
│   └── trying_to_setup_remo_7e17c ↟ : Trying to setup remote
│       └── bump_bazel_version_f8c99 ↟ (Current) : Bump bazel version
├── liliypond_f16c6 ↟ https://github.com/juanique/monorepo/pull/106: liliypond
└── bump_mypy_version_6a97e ↟ https://github.com/juanique/monorepo/pull/112: Bump mypy version.

dont_rebase/upload_c_2f8ff was already merged.

Running gg upload --all fails with:

Traceback (most recent call last):
  File "/app/salsa/gg/gg_cli.runfiles/monorepo/salsa/gg/gg_cli.py", line 199, in <module>
    cli()
  File "/app/salsa/gg/gg_cli.runfiles/pip_deps/pypi__click/click/core.py", line 1130, in __call__
    return self.main(*args, **kwargs)
  File "/app/salsa/gg/gg_cli.runfiles/pip_deps/pypi__click/click/core.py", line 1055, in main
    rv = self.invoke(ctx)
  File "/app/salsa/gg/gg_cli.runfiles/pip_deps/pypi__click/click/core.py", line 1657, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))                                                                                                                                                        File "/app/salsa/gg/gg_cli.runfiles/pip_deps/pypi__click/click/core.py", line 1404, in invoke
    return ctx.invoke(self.callback, **ctx.params)                                                                                                                                                                 File "/app/salsa/gg/gg_cli.runfiles/pip_deps/pypi__click/click/core.py", line 760, in invoke
    return __callback(*args, **kwargs)
  File "/app/salsa/gg/gg_cli.runfiles/monorepo/salsa/gg/gg_cli.py", line 31, in upload
    gg.upload(all_commits=all_)
  File "/app/salsa/gg/gg_cli.runfiles/monorepo/salsa/gg/gg.py", line 494, in upload
    self.traverse(self.root().id, f, skip=False)
  File "/app/salsa/gg/gg_cli.runfiles/monorepo/salsa/gg/gg.py", line 787, in traverse
    self.traverse(c, func)
  File "/app/salsa/gg/gg_cli.runfiles/monorepo/salsa/gg/gg.py", line 787, in traverse
    self.traverse(c, func)
  File "/app/salsa/gg/gg_cli.runfiles/monorepo/salsa/gg/gg.py", line 784, in traverse
    func(commit)
  File "/app/salsa/gg/gg_cli.runfiles/monorepo/salsa/gg/gg.py", line 492, in f
    self.upload(commit_id=c.id)
  File "/app/salsa/gg/gg_cli.runfiles/monorepo/salsa/gg/gg.py", line 521, in upload
    commit.pull_request = self.hosted_repo.create_pull_request(
  File "/app/salsa/gg/gg_cli.runfiles/monorepo/salsa/gg/gg.py", line 279, in create_pull_request
    pr = repo.create_pull(
  File "/app/salsa/gg/gg_cli.runfiles/pip_deps/pypi__pygithub/github/Repository.py", line 1348, in create_pull
    return self.__create_pull_1(*args, **kwds)
  File "/app/salsa/gg/gg_cli.runfiles/pip_deps/pypi__pygithub/github/Repository.py", line 1379, in __create_pull_1
    return self.__create_pull(
  File "/app/salsa/gg/gg_cli.runfiles/pip_deps/pypi__pygithub/github/Repository.py", line 1392, in __create_pull
    headers, data = self._requester.requestJsonAndCheck(
  File "/app/salsa/gg/gg_cli.runfiles/pip_deps/pypi__pygithub/github/Requester.py", line 353, in requestJsonAndCheck
    return self.__check(
  File "/app/salsa/gg/gg_cli.runfiles/pip_deps/pypi__pygithub/github/Requester.py", line 378, in __check
    raise self.__createException(status, responseHeaders, output)
github.GithubException.GithubException: 422 {"message": "Validation Failed", "errors": [{"resource": "PullRequest", "field": "base", "code": "invalid"}], "documentation_url": "https://docs.github.com/rest/ref$rence/pulls#create-a-pull-request"}