Merge branch 'redesign-2024' into redesign/practice-quizzes

Author: jacbn

src/app/components/content/IsaacAccordion.tsx

@@ -183,7 +183,7 @@ export const IsaacAccordion = ({doc}: {doc: ContentDTO}) => {
                 {isPhy && stageInserts?.[index] && <StageInsert stage={stageInserts[index]} />}
                 <Accordion
                     key={`${section.sectionIndex} ${index}`} id={section.id} index={index}
-                    startOpen={section.startOpen || !isDefined(firstSectionToOpen) ? undefined : index === firstSectionToOpen} /* use default <Accordion/> startOpen behaviour if behaviour undefined */
+                    startOpen={section.startOpen ?? !isDefined(firstSectionToOpen) ? undefined : index === firstSectionToOpen} /* use default <Accordion/> startOpen behaviour if behaviour undefined */
                     deEmphasised={section.deEmphasised}
                     trustedTitle={section?.title || ""}
                     audienceString={audienceString}