fix: circuvent meilisearch bug with empty objects #628

Job	Run time
collect-and-verify	4m 22s
lms-1(py=3.11,dj=pinned,mongo=7.0)	10m 7s
lms-2(py=3.11,dj=pinned,mongo=7.0)	11m 28s
lms-3(py=3.11,dj=pinned,mongo=7.0)	10m 22s
lms-4(py=3.11,dj=pinned,mongo=7.0)	10m 6s
lms-5(py=3.11,dj=pinned,mongo=7.0)	9m 22s
lms-6(py=3.11,dj=pinned,mongo=7.0)	9m 23s
openedx-1-with-lms(py=3.11,dj=pinned,mongo=7.0)	8m 35s
openedx-2-with-lms(py=3.11,dj=pinned,mongo=7.0)	7m 47s
openedx-1-with-cms(py=3.11,dj=pinned,mongo=7.0)	8m 26s
openedx-2-with-cms(py=3.11,dj=pinned,mongo=7.0)	7m 1s
cms-1(py=3.11,dj=pinned,mongo=7.0)	6m 21s
cms-2(py=3.11,dj=pinned,mongo=7.0)	12m 31s
common-with-lms(py=3.11,dj=pinned,mongo=7.0)	10m 13s
common-with-cms(py=3.11,dj=pinned,mongo=7.0)	5m 36s
xmodule-with-lms(py=3.11,dj=pinned,mongo=7.0)	7m 31s
xmodule-with-cms(py=3.11,dj=pinned,mongo=7.0)	7m 41s
Unit tests successful	5s
coverage	0s
compile-warnings-report	0s
merge-artifacts	0s
	2h 26m 57s

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