fix: don't break indexing on non-existant course

[Kelketek]

This PR fixes an issue where indexing courses which have been tombstoned crashes. A fix already exists for this upstream, so this is a semantic backport. It can be dropped when upgrading to Verawood.

Internal ticket: https://tasks.opencraft.com/browse/BB-10959

[tecoholic]

@Kelketek 👍 (Conditionally that the tests are fixed)

• I tested this: Created a dummy course
• I read through the code
• I checked for accessibility issues - NA
• Includes documentation

---

Code to create a dummy course for local testing. (AI disclosure: quickly generated using Claude Fable 5)

from opaque_keys.edx.keys import CourseKey
from openedx.core.djangoapps.content.course_overviews.models import CourseOverview

key = CourseKey.from_string("course-v1:Bogus+AdminTest+run1")
CourseOverview.objects.create(
    id=key,
    version=CourseOverview.VERSION,                      # NOT NULL column, no default
    _location=key.make_usage_key("course", "course"),    # NOT NULL column
    display_name="Bogus Tombstone",
)

[tecoholic]

It looks like the test is indented one level too deep and there was a typo in the @patch.

Suggested change

	@override_settings(MEILISEARCH_ENABLED=True)
	@patch('openeedx.core.djangoapps.content.search.api.log')
	def test_graceful_handling_of_missing_course(self, mock_log, _mock_meilisearch) -> None:
	key = CourseKey.from_string('course-v1:Bogus+CourseX+BogoCourse')
	assert api.index_course(key) == [] # pylint: disable=use-implicit-booleaness-not-comparison
	mock_log.error.assert_called_with("Course not found with key: %s", key)
	@override_settings(MEILISEARCH_ENABLED=True)
	@patch('openedx.core.djangoapps.content.search.api.log')
	def test_graceful_handling_of_missing_course(self, mock_log, _mock_meilisearch) -> None:
	key = CourseKey.from_string('course-v1:Bogus+CourseX+BogoCourse')
	assert api.index_course(key) == [] # pylint: disable=use-implicit-booleaness-not-comparison
	mock_log.error.assert_called_with("Course not found with key: %s", key)