Only add the app-itunes-app tag if the id is set

Signed-off-by: Julius Härtl <jus@bitgrid.net>

core/templates/layout.guest.php

@@ -11,7 +11,9 @@
 		</title>
 		<meta http-equiv="X-UA-Compatible" content="IE=edge">
 		<meta name="viewport" content="width=device-width, initial-scale=1.0, minimum-scale=1.0">
+		<?php if ($theme->getiTunesAppId() !== '') { ?>
 		<meta name="apple-itunes-app" content="app-id=<?php p($theme->getiTunesAppId()); ?>">
+		<?php } ?>
 		<meta name="theme-color" content="<?php p($theme->getColorPrimary()); ?>">
 		<link rel="icon" href="<?php print_unescaped(image_path('', 'favicon.ico')); /* IE11+ supports png */ ?>">
 		<link rel="apple-touch-icon" href="<?php print_unescaped(image_path('', 'favicon-touch.png')); ?>">

core/templates/layout.public.php

@@ -10,7 +10,9 @@
 	</title>
 	<meta http-equiv="X-UA-Compatible" content="IE=edge">
 	<meta name="viewport" content="width=device-width, initial-scale=1.0, minimum-scale=1.0">
+	<?php if ($theme->getiTunesAppId() !== '') { ?>
 	<meta name="apple-itunes-app" content="app-id=<?php p($theme->getiTunesAppId()); ?>">
+	<?php } ?>
 	<meta name="apple-mobile-web-app-capable" content="yes">
 	<meta name="apple-mobile-web-app-status-bar-style" content="black">
 	<meta name="apple-mobile-web-app-title" content="<?php p((!empty($_['application']) && $_['appid']!=='files')? $_['application']:$theme->getTitle()); ?>">

core/templates/layout.user.php

@@ -10,7 +10,9 @@
 		</title>
 		<meta http-equiv="X-UA-Compatible" content="IE=edge">
 		<meta name="viewport" content="width=device-width, initial-scale=1.0, minimum-scale=1.0">
+		<?php if ($theme->getiTunesAppId() !== '') { ?>
 		<meta name="apple-itunes-app" content="app-id=<?php p($theme->getiTunesAppId()); ?>">
+		<?php } ?>
 		<meta name="apple-mobile-web-app-capable" content="yes">
 		<meta name="apple-mobile-web-app-status-bar-style" content="black">
 		<meta name="apple-mobile-web-app-title" content="<?php p((!empty($_['application']) && $_['appid']!='files')? $_['application']:$theme->getTitle()); ?>">