fix: circuvent meilisearch bug with empty objects #630

Job	Run time
collect-and-verify	3m 58s
lms-1(py=3.11,dj=pinned,mongo=7.0)	9m 31s
lms-2(py=3.11,dj=pinned,mongo=7.0)	7m 43s
lms-3(py=3.11,dj=pinned,mongo=7.0)	7m 22s
lms-4(py=3.11,dj=pinned,mongo=7.0)	7m 12s
lms-5(py=3.11,dj=pinned,mongo=7.0)	7m 7s
lms-6(py=3.11,dj=pinned,mongo=7.0)	6m 44s
openedx-1-with-lms(py=3.11,dj=pinned,mongo=7.0)	5m 31s
openedx-2-with-lms(py=3.11,dj=pinned,mongo=7.0)	4m 50s
openedx-1-with-cms(py=3.11,dj=pinned,mongo=7.0)	6m 1s
openedx-2-with-cms(py=3.11,dj=pinned,mongo=7.0)	4m 57s
cms-1(py=3.11,dj=pinned,mongo=7.0)	6m 24s
cms-2(py=3.11,dj=pinned,mongo=7.0)	11m 6s
common-with-lms(py=3.11,dj=pinned,mongo=7.0)	9m 33s
common-with-cms(py=3.11,dj=pinned,mongo=7.0)	5m 37s
xmodule-with-lms(py=3.11,dj=pinned,mongo=7.0)	4m 50s
xmodule-with-cms(py=3.11,dj=pinned,mongo=7.0)	4m 50s
Unit tests successful	4s
compile-warnings-report	0s
coverage	0s
merge-artifacts	0s
	1h 53m 20s

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