Resolve "Add export functionality to course book"

Closes #258 (closed)

aleksis/apps/alsijil/frontend/components/coursebook/Coursebook.vue

@@ -56,7 +56,7 @@
           :subjects="subjects"
           :documentation="item"
           :affected-query="lastQuery"
-          :value="(selectedParticipations[item.id] ??= [])"
+          :value="selectedParticipations[item.id] ??= []"
           @input="selectParticipation(item.id, $event)"
         />
       </template>