fix: error when saving changes to a v2 library block (#35217) #27425

Job	Run time
collect-and-verify	6m 12s
lms-1(py=3.11,dj=pinned,mongo=7.0)	10m 37s
lms-2(py=3.11,dj=pinned,mongo=7.0)	12m 48s
lms-3(py=3.11,dj=pinned,mongo=7.0)	15m 5s
lms-4(py=3.11,dj=pinned,mongo=7.0)	21m 16s
lms-5(py=3.11,dj=pinned,mongo=7.0)	11m 37s
lms-6(py=3.11,dj=pinned,mongo=7.0)	15m 50s
openedx-1-with-lms(py=3.11,dj=pinned,mongo=7.0)	11m 24s
openedx-2-with-lms(py=3.11,dj=pinned,mongo=7.0)	15m 59s
openedx-1-with-cms(py=3.11,dj=pinned,mongo=7.0)	8m 39s
openedx-2-with-cms(py=3.11,dj=pinned,mongo=7.0)	6m 59s
cms-1(py=3.11,dj=pinned,mongo=7.0)	5m 33s
cms-2(py=3.11,dj=pinned,mongo=7.0)	12m 33s
common-with-lms(py=3.11,dj=pinned,mongo=7.0)	10m 59s
common-with-cms(py=3.11,dj=pinned,mongo=7.0)	6m 22s
xmodule-with-lms(py=3.11,dj=pinned,mongo=7.0)	6m 42s
xmodule-with-cms(py=3.11,dj=pinned,mongo=7.0)	7m 4s
coverage (3.11)	1m 45s
Unit tests successful	2s
compile-warnings-report	11s
merge-artifacts	8s
	3h 7m 45s

Provide feedback