fix: return empty list when no courses are found for request #32310

Job	Run time
lms-1(py=3.11,dj=pinned,mongo=7.0)	10m 9s
lms-2(py=3.11,dj=pinned,mongo=7.0)	12m 7s
lms-3(py=3.11,dj=pinned,mongo=7.0)	15m 27s
lms-4(py=3.11,dj=pinned,mongo=7.0)	20m 7s
lms-5(py=3.11,dj=pinned,mongo=7.0)	11m 9s
lms-6(py=3.11,dj=pinned,mongo=7.0)	16m 14s
openedx-1-with-lms(py=3.11,dj=pinned,mongo=7.0)	11m 1s
openedx-2-with-lms(py=3.11,dj=pinned,mongo=7.0)	14m 46s
openedx-1-with-cms(py=3.11,dj=pinned,mongo=7.0)	8m 40s
openedx-2-with-cms(py=3.11,dj=pinned,mongo=7.0)	6m 33s
cms-1(py=3.11,dj=pinned,mongo=7.0)	4m 47s
collect-and-verify	4m 23s
cms-2(py=3.11,dj=pinned,mongo=7.0)	13m 1s
common-with-lms(py=3.11,dj=pinned,mongo=7.0)	9m 24s
common-with-cms(py=3.11,dj=pinned,mongo=7.0)	5m 28s
xmodule-with-lms(py=3.11,dj=pinned,mongo=7.0)	8m 56s
xmodule-with-cms(py=3.11,dj=pinned,mongo=7.0)	8m 48s
Unit tests successful	4s
compile-warnings-report	9s
coverage	0s
merge-artifacts	7s
	3h 1m 20s

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