code: public void setEmptyText(CharSequence text) {
          ensureList();
          if (mStandardEmptyView == null) {
              throw new IllegalStateException("Can't be used with a custom content view");
          }
          mStandardEmptyView.setText(text);
          if (mEmptyText == null) {
              mList.setEmptyView(mStandardEmptyView);
          }
          mEmptyText = text;
      }
docs: The default content for a ListFragment has a TextView that can
  be shown when the list is empty.  If you would like to have it
  shown, call this method to supply the text it should use.