Returns the String to use as an error dialog message for
	 * a failed action. This message appears as the "Message:" in
	 * the error dialog for this action.
	 * Default is to return null.
Returns the String to use as an error dialog message for
	 * a failed action. This message appears as the "Message:" in
	 * the error dialog for this action.
	 * Default is to return null. | AbstractDebugActionDelegate.java