PostmanState.php::isTimeToReviewPostman() should always return a boolean value

[IanDelMar]

If the condition on line 63 fails, PostmanState.php::isTimeToReviewPostman() does not return a boolean value.

Post-SMTP/Postman/PostmanState.php

Lines 62 to 68 in afce560

	public function isTimeToReviewPostman() {
	if (! empty ( $this->options [self::INSTALL_DATE] )) {
	$successful = PostmanState::getInstance ()->getSuccessfulDeliveries () > 0;
	$maxTime = $this->options [self::INSTALL_DATE] + self::TOO_LONG_SEC;
	return $successful && time () <= $maxTime;
	}
	}