[5.3] undefined array key in table\nested.php (joomla#45176)

Author: brianteeman

libraries/src/Table/Nested.php

@@ -1317,7 +1317,7 @@ public function rebuildPath($pk = null)
         $segments = $this->_db->loadColumn();
 
         // Make sure to remove the root path if it exists in the list.
-        if ($segments[0] === 'root') {
+        if (!empty($segments) && $segments[0] === 'root') {
             array_shift($segments);
         }