MOBILE-4081 tag: Do not select any tag if on mobile view

src/core/components/split-view/split-view.scss

@@ -74,6 +74,7 @@
     --menu-border-width: 0px;
     --menu-box-shadow: none;
     --menu-z: 0px;
+    --selected-item-border-width: 0px;
     --selected-item-color: transparent;
 }
 

src/core/features/tag/pages/index/index.page.ts

@@ -43,7 +43,7 @@ export class CoreTagIndexPage implements OnInit {
     areas: CoreTagAreaDisplay[] = [];
 
     /**
-     * View loaded.
+     * @inheritdoc
      */
     async ngOnInit(): Promise<void> {
         this.tagId = CoreNavigator.getRouteNumberParam('tagId') || this.tagId;
@@ -143,7 +143,14 @@ export class CoreTagIndexPage implements OnInit {
      * @param area Area.
      */
     openArea(area: CoreTagAreaDisplay): void {
+        if (area.id === this.selectedAreaId) {
+            // Already opened.
+            return;
+        }
+
+        if (CoreScreen.isTablet) {
             this.selectedAreaId = area.id;
+        }
 
         const params = {
             tagId: this.tagId,