Issue#2535: Hide add more button in submission if no disabled sections

(cherry picked from commit 709848e)

src/app/submission/form/section-add/submission-form-section-add.component.html

@@ -3,13 +3,14 @@
      placement="bottom-right"
      class="d-inline-block"
      [ngClass]="{'w-100': windowService.isXs()}">
+  <ng-container *ngIf="hasSections$ | async">
   <button class="btn btn-outline-primary dropdown-toggle"
           id="sectionControls"
-          [disabled]="!(hasSections$ | async)"
           [ngClass]="{'w-100': (windowService.isXs() | async)}"
           ngbDropdownToggle>
           {{ 'submission.sections.general.add-more' | translate }} <i class="fa fa-plus" aria-hidden="true"></i>
   </button>
+  </ng-container>
   <div ngbDropdownMenu
        class="sections-dropdown-menu"
        aria-labelledby="sectionControls"