fix BookingCodesMessage:sendMessage() wrong $attachment for prepareMail

prepareMail expects an associative array or null as $attachment, but sendMessage passed a associate array inside a array (which was actually working due to magic in Message::addStringAttachments) or null inside an array, for the case where an ical-attachment is not to be sent. The [null] was misunderstood by SendNotificationMail() as a mail with an attachment, calling phpmailer with illegal parameters and causing warnings. The mail was seemingly send anyway, totally expected without attachment. So the change is a fix to avoid warnings, but it does not change the behavior for the user in any way.

Additionally, add two more tests to cover the (non-default) case when sending of ical-attachment for BookingCodes is ON

src/Messages/BookingCodesMessage.php

@@ -95,7 +95,7 @@ public function sendMessage(): bool {
                 'item' => $timeframe->getItem(),
                 'location' => $timeframe->getLocation(),
             ],
-            [ $attachment]
+			$attachment
 		);
 
         add_action( 'commonsbooking_mail_sent',array($this,'updateEmailSent'), 5, 2 );

tests/php/Service/BookingCodesTest.php

@@ -43,6 +43,15 @@ public function testSendBookingCodesMessage() {
 		$this->assertMatchesRegularExpression('/' . implode('|',self::bookingCodes) . '/',$email->get_sent()->body);
 	}
 
+	/* As testSendBookingCodesMessage but cover the case when Ical is attached */
+	public function testSendBookingCodesMessageWithICal() {
+
+		// enable sending of Ical attachment
+		Settings::updateOption( 'commonsbooking_options_bookingcodes', 'mail-booking-codes-attach-ical', 'on');
+
+		$this->testSendBookingCodesMessage();
+	}
+
 	/* Tests some exceptional calculations for emailing booking codes (range and next event) */
 	public function testGetCronParams() {
 		$this->setCronParams(strtotime("2020-02-29"),strtotime("2023-01-15"));

tests/php/View/BookingCodesTest.php

@@ -51,6 +51,13 @@ public function testEmailCodes() {
 		$this->assertMatchesRegularExpression('/' . implode('|',self::bookingCodes) . '/',$email->get_sent()->body);
 	}
 
+	/* As above but cover the case when ical is attached */
+	public function testEmailCodesWithIcal() {
+
+		Settings::updateOption( 'commonsbooking_options_bookingcodes', 'mail-booking-codes-attach-ical', 'on');
+
+		$this->testEmailCodes();
+	}
 
 	public function testInitialCronEmailEvent() {
 		$todayDate = new \DateTime(self::CURRENT_DATE);