message: Add missing parens to fix "unavailable" translation
diff: class="{{challenge.disabledEnv ? ('fab fa-' + challenge.disabledEnv?.toLowerCase()) : (challenge.solved ? 'far fa-flag' : 'fas fa-book')}}"
  aria-hidden="true"
  [hidden]="!challenge.disabledEnv && ((challenge.solved && !allowRepeatNotifications) || (!challenge.solved && (!showChallengeHints || !(challenge.hint || challenge.hintUrl))))"></i>
  - {{challenge.disabledEnv ? "STATUS_UNAVAILABLE" : (challenge.solved ? "STATUS_SOLVED" : "STATUS_UNSOLVED") | translate}}
  + {{(challenge.disabledEnv ? "STATUS_UNAVAILABLE" : (challenge.solved ? "STATUS_SOLVED" : "STATUS_UNSOLVED")) | translate}}
  </span>
  </button>
  </mat-cell>
  