fix: return empty list when no courses are found for request #32295

Job	Run time
collect-and-verify	4m 19s
lms-1(py=3.11,dj=pinned,mongo=7.0)	10m 45s
lms-2(py=3.11,dj=pinned,mongo=7.0)	12m 31s
lms-3(py=3.11,dj=pinned,mongo=7.0)	15m 13s
lms-4(py=3.11,dj=pinned,mongo=7.0)	20m 38s
lms-5(py=3.11,dj=pinned,mongo=7.0)	11m 13s
lms-6(py=3.11,dj=pinned,mongo=7.0)	16m 20s
openedx-1-with-lms(py=3.11,dj=pinned,mongo=7.0)	11m 56s
openedx-2-with-lms(py=3.11,dj=pinned,mongo=7.0)	14m 33s
openedx-1-with-cms(py=3.11,dj=pinned,mongo=7.0)	8m 36s
openedx-2-with-cms(py=3.11,dj=pinned,mongo=7.0)	7m 8s
cms-1(py=3.11,dj=pinned,mongo=7.0)	5m 28s
cms-2(py=3.11,dj=pinned,mongo=7.0)	13m 15s
common-with-lms(py=3.11,dj=pinned,mongo=7.0)	9m 46s
common-with-cms(py=3.11,dj=pinned,mongo=7.0)	5m 40s
xmodule-with-lms(py=3.11,dj=pinned,mongo=7.0)	8m 38s
xmodule-with-cms(py=3.11,dj=pinned,mongo=7.0)	8m 50s
xmodule-with-cms(py=3.11,dj=pinned,mongo=7.0)	8m 41s
xmodule-with-lms(py=3.11,dj=pinned,mongo=7.0)	8m 32s
Unit tests successful	2s
coverage (3.11)	1m 49s
compile-warnings-report	9s
merge-artifacts	7s
	3h 24m 9s

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