only show disable all keys if enabled

src/app/settings/two-factor-yubikey.component.html

@@ -59,7 +59,7 @@
                         <span>{{'save' | i18n}}</span>
                     </button>
                     <button #disableBtn type="button" class="btn btn-outline-secondary btn-submit" [appApiAction]="disablePromise" [disabled]="disableBtn.loading"
-                        (click)="disable()">
+                        (click)="disable()" *ngIf="enabled">
                         <i class="fa fa-spinner fa-spin" title="{{'loading' | i18n}}"></i>
                         <span>{{'disableAllKeys' | i18n}}</span>
                     </button>