message: Hide hacking instructor on disabled challenges
diff: <i class="fa-2x fas fa-exclamation-circle" aria-hidden="true"></i> {{"BTN_SHOW_DISABLED" | translate}}
  </mat-button-toggle>
  - <div *ngIf="showDisabledChallenges" class="disabled-challenges-infoBox mat-button" [innerHTML]="'INFO_DISABLED_CHALLENGES' | translate: {num: numDisabledChallenges, env: disabledEnv}"></div>
  + <div *ngIf="numDisabledChallenges > 0 && showDisabledChallenges" class="disabled-challenges-infoBox mat-button" [innerHTML]="'INFO_DISABLED_CHALLENGES' | translate: {num: numDisabledChallenges, env: disabledEnv}"></div>
  </div>
  <mat-divider></mat-divider>
  [showChallengeHints]="showChallengeHints">
  </app-challenge-status-badge>
  <button
  - *ngIf="showHackingInstructor && challenge.hasTutorial"
  + *ngIf="showHackingInstructor && !challenge.disabledEnv && challenge.hasTutorial"
  mat-raised-button color="warn"
  (click)="startHackingInstructor(challenge.name)"
  [matTooltip]="('INFO_HACKING_INSTRUCTOR' | translate)"
  