Feature/request history

src/app/datasets/datasets.component.html

@@ -3,10 +3,13 @@
 
   <mat-sidenav #sidenav mode="side" position="end" opened id="request-historical">
     <h6 id="history-title">Request history</h6>
-    <nb-list id="history-list">
+    <nb-list id="history-list" *ngIf="requestHistorical != null && requestHistorical.length > 0; else noHistory">
       <nb-list-item *ngFor="let request of requestHistorical"><a [href]="request" target="_blank"
           rel="noreferrer noopener">{{request}}</a></nb-list-item>
     </nb-list>
+    <ng-template #noHistory>
+      <p id="no-history-found-message">No history found...</p>
+    </ng-template>
   </mat-sidenav>