message: fix ts compilation error with mismatched arguments
diff: <div class="row">
  <div class="col s12">
  <div class="input-field">
  - <i class="material-icons prefix search" (click)="getUsersByKeyword(searchTerm.value)">search</i>
  - <input type="text" #searchTerm materialize="autocomplete" [materializeParams]="keywords" (keyup.enter)="getUsersByKeyword(searchTerm.value)"
  + <i class="material-icons prefix search" (click)="getUsersByKeyword(searchTerm.value, null, null)">search</i>
  + <input type="text" #searchTerm materialize="autocomplete" [materializeParams]="keywords" (keyup.enter)="getUsersByKeyword(searchTerm.value, null, null)"
  id="autocomplete-input" class="autocomplete">
  <label for="autocomplete-input">search volunteers</label>
  