遇到错误无法找到您指定的模型:user

When I set DB password on application/config/database.php, then showing me an error message.

An Error Was Encountered Unable to locate the model you have specified: user

If not set password, its showing me:

Filename: core/Loader.php

Line Number: 346

$active_group = 'default';
$active_record = TRUE;

$db['default']['hostname'] = 'localhost';
$db['default']['username'] = 'masudtools_auto';
$db['default']['password'] = 'password';
$db['default']['database'] = 'masudtools_post';
$db['default']['dbdriver'] = 'mysql';
$db['default']['dbprefix'] = '';
$db['default']['pconnect'] = FALSE;
$db['default']['db_debug'] = TRUE;
$db['default']['cache_on'] = FALSE;
$db['default']['cachedir'] = '';
$db['default']['char_set'] = 'utf8';
$db['default']['dbcollat'] = 'utf8_general_ci';
$db['default']['swap_pre']= '';
$db['default']['autoinit'] = TRUE;
$db['default']['stricton'] = FALSE;

/*USER DB*/
$db['second']['hostname'] = 'localhost';
$db['second']['username'] = 'masudtools_auto';
$db['second']['password'] = 'password';
$db['second']['database'] = 'masudtools_post';
$db['second']['dbdriver'] = 'mysql';
$db['second']['dbprefix'] = '';
$db['second']['pconnect'] = TRUE;
$db['second']['db_debug'] = TRUE;
$db['second']['cache_on'] = FALSE;
$db['second']['cachedir'] = '';
$db['second']['char_set'] = 'utf8';
$db['second']['dbcollat'] = 'utf8_general_ci';
$db['second']['swap_pre'] = '';
$db['second']['autoinit'] = TRUE;
$db['second']['stricton'] = FALSE;

Please help me to solve this problem.

What is meant by model here? is it CI model or any other, if it is CI model check weather you have extended it with CI_Model and relevant databases are loaded to model