Fix oldId handling

aleksis/apps/alsijil/frontend/components/coursebook/documentation/LessonSummary.vue

@@ -119,11 +119,11 @@ export default {
             (o) => o[itemId] === this.documentation.id,
           );
           // merged with the incoming partial documentation
-          // set ID of documentation currently being edited as oldID so that key in coursebook doesn't change
+          // if creation of proper documentation from dummy one, set ID of documentation currently being edited as oldID so that key in coursebook doesn't change
           cached[index] = {
             ...this.documentation,
             ...object,
-            oldId: this.documentation.id,
+            oldId: this.documentation.id !== object.id ? this.documentation.id : this.documentation.oldId,
           };
         }
         return cached;