Add comment and check if parameters are set

src/Jenssegers/Mongodb/Connection.php

@@ -136,8 +136,9 @@ class Connection extends \Illuminate\Database\Connection
             $driverOptions = $config['driver_options'];
         }
         
-        $options['username'] = $config['username'];
-        $options['password'] = $config['password'];
+        // Get the credentials from the config and check if they are set
+        $options['username'] = isset($options['username']) ? $config['username'] : '';
+        $options['password'] = isset($options['password']) ? $config['password'] : '';
 
         return new Client($dsn, $options, $driverOptions);
     }