Don't delete parent directories

includes/functions/deleteDirectory.php

@@ -9,6 +9,10 @@
 function delete_directory(string $directoryToDelete)
 {
     foreach (scandir($directoryToDelete) as $filename) {
+        if (in_array($filename, array('.', '..'))) {
+            continue;
+        }
+
         $filepath = $directoryToDelete . '/' . $filename;
 
         if (is_file($filepath)) {