remove a js error when a variable is not initialised

src/app/login/login.component.html

@@ -28,7 +28,7 @@
                         </div>
                         <div fxLayout="row" fxLayoutAlign="space-around center" style="width: 100%">
                             <button mat-flat-button (click)="login()" color=primary style="width: 25%; text-align: center">Login</button>
-                            <button *ngIf="(authService.loggedInAuthZ | async).length > 0" mat-flat-button  routerLink="/launch" color=warn style="width: 25%; text-align: center">Cancel</button>
+                            <button *ngIf="(authService.loggedInAuthZ | async) != null && (authService.loggedInAuthZ | async).length > 0" mat-flat-button  routerLink="/launch" color=warn style="width: 25%; text-align: center">Cancel</button>
                         </div>
                         <div *ngIf="selected !== undefined" [innerHTML]="selected.desc">
                         </div>