<ng-template *ngIf="enableValidation(param.boolean)">
     <a href="{{param.link}}">
        <clr-icon shape="info-standard"></clr-icon> Acceder
       </a>
 </ng-template>

enableValidation(exist: any) {
        if (exist === null) {
            return true;
        }
    }

<div *ngIf="{{param.boolean}} === null ; else myData" >   </div>
     <ng-template #myData>
        <a href="{{param.link}}">
        <clr-icon shape="info-standard"></clr-icon> Acceder
          </a>
      </ng-template>