Update section item when inserting sections

When inserting a section at the beginning of the entry, we need to
update the transition of the previously first section. Also the
section might no longer be the active section, even though
currentSectionIndex did not change.

REDMINE-20217

entry_types/scrolled/package/src/editor/views/SectionItemView.js

@@ -68,6 +68,11 @@ export const SectionItemView = Marionette.ItemView.extend({
         });
       }
     });
+
+    this.listenTo(this.options.entry.sections, 'add', () => {
+      this.updateActive();
+      this.updateTransition();
+    });
   },
 
   onRender() {
@@ -78,10 +83,6 @@ export const SectionItemView = Marionette.ItemView.extend({
     }
 
     this.$el.toggleClass(styles.invert, !!this.model.configuration.get('invert'));
-    this.ui.transition.text(
-      I18n.t(this.getTransition(),
-             {scope: 'pageflow_scrolled.editor.section_item.transitions'})
-    );
 
     this.subview(new SectionThumbnailView({
       el: this.ui.thumbnail,