message: disabled buttons and changed the no files message accordingly.
diff: <div class="spacer">
  <div class="selectArea">
  - <button mat-raised-button color="secondary" (click)="listview()" mat-tooltip="List View" class="btn"
  + <button mat-raised-button color="secondary" [disabled]="!checkForFileUnits()" (click)="listview()" mat-tooltip="List View" class="btn"
  [class.activeBtn]="displayGrid==false">
  <i class="material-icons iconSize">view_list</i> List
  </button>
  - <button mat-raised-button color="secondary" (click)="gridview()"
  + <button mat-raised-button color="secondary" [disabled]="!checkForFileUnits()" (click)="gridview()"
  mat-tooltip="Grid View" class="btn" [class.activeBtn]="displayGrid==true">
  <i class="material-icons iconSize">view_module</i> Grid
  </button>
  </div>
  </div>
  <div *ngIf="!checkForFileUnits()">
  - <h2>There are no Files Attached to this course yet!</h2>
  + <h2>There are no Videos Attached to this course yet!</h2>
  </div>
  