fix display sign list

src/frontend/app/profile/profile.component.html

@@ -256,7 +256,7 @@
                                         </mat-form-field>
                                     </div>
                                 </div>
-                                <fieldset *ngIf="profileInfo.substitute != null">
+                                <fieldset *ngIf="profileInfo.substitute != null && signaturesService.signaturesList.length > 0">
                                     <legend align="left">{{'lang.signSubstituted' | translate}} :</legend>
                                     <ng-container>
                                         <button type="button" class="signListButton" mat-stroked-button *ngFor="let signature of signaturesService.signaturesList; let i=index" (click)="toggleSignature(i)" [class.selected]="signature.substituted"><img [src]="sanitizer.bypassSecurityTrustUrl('data:image/png;base64,' + signature.encodedSignature)"/></button>