private static SetupViewModel buildErrorVM(final @StringRes int message, final @Nullable Analytics.Event event) {
		if (event != null) event.send();
		final SetupViewModel next = new SetupViewModel();
		next.message = message;
		next.button_next.set(-1);
		next.action_extra = R.string.button_instructions_online;	// Default extra action, can be overridden by withExtraAction().
		return next;
	}
@return null if all prerequisites met TODO: Move this method to IslandSetup
mobile/src/main/java/com/oasisfeng/island/setup/SetupViewModel.java