fix broker registration

Author: pxpm

src/BackpackServiceProvider.php

@@ -275,7 +275,9 @@ public function loadConfigs()
 
         // add the backpack_users password broker to the configuration
         $laravelAuthPasswordBrokers = app()->config['auth.passwords'];
-        $laravelFirstPasswordBroker = current($laravelAuthPasswordBrokers) ? current($laravelAuthPasswordBrokers)['table'] : '';
+        $laravelFirstPasswordBroker = is_array($laravelAuthPasswordBrokers) && current($laravelAuthPasswordBrokers) ? 
+                                        current($laravelAuthPasswordBrokers)['table'] : 
+                                        '';
 
         $backpackPasswordBrokerTable = config('backpack.base.password_resets_table') ??
                                         config('auth.passwords.users.table') ??