fix: circuvent meilisearch bug with empty objects #627

Job	Run time
collect-and-verify	4m 7s
lms-1(py=3.11,dj=pinned,mongo=7.0)	9m 51s
lms-2(py=3.11,dj=pinned,mongo=7.0)	10m 26s
lms-3(py=3.11,dj=pinned,mongo=7.0)	10m 25s
lms-4(py=3.11,dj=pinned,mongo=7.0)	10m 10s
lms-5(py=3.11,dj=pinned,mongo=7.0)	9m 58s
lms-6(py=3.11,dj=pinned,mongo=7.0)	9m 48s
openedx-1-with-lms(py=3.11,dj=pinned,mongo=7.0)	8m 52s
openedx-2-with-lms(py=3.11,dj=pinned,mongo=7.0)	7m 58s
openedx-1-with-cms(py=3.11,dj=pinned,mongo=7.0)	8m 27s
openedx-2-with-cms(py=3.11,dj=pinned,mongo=7.0)	6m 38s
cms-1(py=3.11,dj=pinned,mongo=7.0)	4m 46s
cms-2(py=3.11,dj=pinned,mongo=7.0)	12m 30s
common-with-lms(py=3.11,dj=pinned,mongo=7.0)	9m 41s
common-with-cms(py=3.11,dj=pinned,mongo=7.0)	5m 28s
xmodule-with-lms(py=3.11,dj=pinned,mongo=7.0)	7m 41s
xmodule-with-cms(py=3.11,dj=pinned,mongo=7.0)	7m 47s
Unit tests successful	1s
compile-warnings-report	0s
coverage	0s
merge-artifacts	0s
	2h 24m 34s

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