title: setMultiChoiceItems() doesn't shows items
body: <p>Im using a <strong>DialogFragment</strong> to show a Dialog with a multi choice items, it shows the Dialog but without the items, there is no checkboxes to select.</p>
  
  <p>This is how i invoke the dialog:</p>
  
  <pre><code>    botAddMedicacion.setOnClickListener(new View.OnClickListener() {
          @Override
          public void onClick(View v) {
              DialogFragment fragAddMedic = new AnadirMedicacionFragment();
              fragAddMedic.show(getFragmentManager(), "addMedicacion");
          }
      });
  </code></pre>
  
  <p>And this is the <strong>AnadirMedicacionFragment</strong> code:</p>
  
  <pre><code>    final CharSequence[] items={".NET","J2EE","PHP"};
  
  @Override
  public Dialog onCreateDialog(Bundle savedInstanceState){
  
      medicSelec = new ArrayList();
  
      AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
      builder.setMessage(R.string.anadir_medicacion);
  
  
      // elementos de la lista
      builder.setMultiChoiceItems(items, null, new DialogInterface.OnMultiChoiceClickListener() {
          @Override
          public void onClick(DialogInterface dialog, int which, boolean isChecked) {
  
              if (isChecked) {
                  medicSelec.add(which);
              } else if (medicSelec.contains(which)) {
                  medicSelec.remove(Integer.valueOf(which));
              }
  
          }
      });
  
      // boton ok
      builder.setPositiveButton(R.string.anadir, new DialogInterface.OnClickListener(){
          @Override
          public void onClick(DialogInterface dialog, int which) {
  
          }
      });
  
      // boton cancelar
      builder.setNegativeButton(R.string.cancelar, new DialogInterface.OnClickListener(){
          @Override
          public void onClick(DialogInterface dialog, int which) {
  
          }
      });
  
      return builder.create();
  }
  </code></pre>
  
  <p>The item list is passed in builder.setMultiChoiceItems(<strong>items</strong>, null[...]</p>
  
  <p><img src="https://i.stack.imgur.com/ieEjA.png" alt="dialog fragment multi choose"></p>
  
  <p>It seems it works, but there are no checkboxes or list.</p>