[BUGFIX] SQL error for mountpoints with no subpages

If a mountpoint has no subpages and the mountpoint page itsself is
not overlayed there are no pages that need to be added to the index.

In that case the SQL queries are skipped which would cause an error
otherwise because of an empty IN() clause.

Resolves: #65282
Change-Id: Ibdf00259c895596281084866cbf9285afaf22063

Conflicts:
	Classes/IndexQueue/Initializer/Page.php

Author: Alexander Stehlik

Classes/IndexQueue/Initializer/Page.php

@@ -132,6 +132,12 @@ protected function initializeMountPages() {
 				);
 			}
 
+			// This can happen when the mount point does not show the content of the
+			// mounted page and the mounted page does not have any subpages.
+			if (empty($mountedPages)) {
+				continue;
+			}
+
 			$this->databaseTransactionStart();
 			try {
 				$this->addMountedPagesToIndexQueue($mountedPages);