Hide scrollable table if its empty (#9811)

* Hide scrollable table if its empty

The scrollable table used to show a scrollbar even if empty, because `overflow-x: scroll;` is set explicitly. Completely
removing the element if it's empty fixes this

frontend/src/app/features/user-preferences/notifications-settings/table/notification-settings-table.component.html

@@ -1,8 +1,8 @@
-<div class="op-scrollable-table">
-  <table
-    class="op-table"
-    *ngIf="settings.length > 0"
-  >
+<div
+  class="op-scrollable-table"
+  *ngIf="settings.length > 0"
+>
+  <table class="op-table">
     <thead>
       <tr>
         <th class="op-table--cell op-table--cell_heading">