Brazenhead issues while trying to invoke the action bar home button

Cucumber console output (partial)

  Scenario: View the navigation menu
    When I expose the navigation menu
      {"exception":"java.lang.reflect.InvocationTargetException","theCause":{"exception":"java.lang.NullPointerException"}} (Exception)
      ./features/step_definitions/screenshot_defs.rb:12:in `/^I expose the navigation menu$/'
      features/screenshots.feature:8:in `When I expose the navigation menu'
    Then I can take a screenshot of the "navigation menu"

screenshot_defs.rb (partial)

When /^I expose the navigation menu$/ do
  # @driver.clickOnActionBarHomeButton     # Doesn't work...NPE
  # @driver.clickOnActionBarHomeButton({:target => 'Robotium'}) #Doesn't work...NPE
  # @driver.click_on_action_bar_item('android.R.id.home') # Doesn't work...string vs res int
  # @driver.click_on_action_bar_home_button() #Doesn't work...NPE
  @driver.click_on_action_bar_home_button #Doesn't work...NPE 
end

Updated BrazenHead com.leandog.brazenhead.commands.CommandRunner method to dump informative information to logcat.

public void execute(final Command... commands) throws Exception {
clearLastRun();

    for (final Command command : commands) {
        try {
            theLastResult = findMethod(command).invoke(theTargetFor(command), theArguments(command));
        } catch (InvocationTargetException ex) {
            Log.e("CommandRunner", "Error while trying to invoke the method " + command.getName(), ex);
            throw ex;
        }

        if (command.hasVariable()) {
            storeVariable(command);
        }
    }
}