## 🐛 Bug Report

Running with java binding and Firefox, the framework occasionally throws NullPointerException on the isDisplayed call.

**Please see https://github.com/mozilla/geckodriver/issues/1825 for more information.** As stated from geckodriver team, the issue is apparently related to the custom JS that is executed with this method. The ticket also contains trace logs. 

## To Reproduce

Hard to provide steps, as it happens "randomly".

## Expected behavior

Should not throw exception..

## Environment

OS: Windows 10
Browser: Firefox
Browser version: 84.0.1
Browser Driver version: geckodriver 0.28.0 (c00d2b6acd3f 2020-11-03 16:29 +0200)
Language Bindings version: java 3.141.59

public String getAriaRole() {
    return stringValueOf(
      execute(DriverCommand.GET_ELEMENT_ARIA_ROLE(id))
        .getValue());
  }
  @Override
  public String getAccessibleName() {
    return stringValueOf(
      execute(DriverCommand.GET_ELEMENT_ACCESSIBLE_NAME(id))
        .getValue());
  }
  private static String stringValueOf(Object o) {
    if (o == null) {
      return null;
    }
    return String.valueOf(o);
  }
  @Override
  public boolean isSelected() {
    Object value = execute(DriverCommand.IS_ELEMENT_SELECTED(id))
      .getValue();
    try {
      return (Boolean) value;
    } catch (ClassCastException ex) {
      throw new WebDriverException("Returned value cannot be converted to Boolean: " + value, ex);
    }
  }
  @Override
  public boolean isEnabled() {
    Object value = execute(DriverCommand.IS_ELEMENT_ENABLED(id))