Only load viewer in settings if the viewer app is enabled

Signed-off-by: Morris Jobke <hey@morrisjobke.de>

apps/settings/lib/Settings/Personal/ServerDevNotice.php

@@ -77,6 +77,9 @@ class ServerDevNotice implements ISettings {
 
 		$hasInitialState = false;
 
+		// viewer is default enabled and this makes a zero-cost assertion for Psalm
+		assert(class_exists(LoadViewer::class));
+
 		// If the Reasons to use Nextcloud.pdf file is here, let's init Viewer
 		if ($userFolder->nodeExists('Reasons to use Nextcloud.pdf')) {
 			$this->eventDispatcher->dispatch(LoadViewer::class, new LoadViewer());