Codeigniter Sending Email Message: strpos(): Empty needle

When sending an email you get this error, regarding Email.php library:

A PHP Error was encountered

Severity: Warning
Message: strpos(): Empty needle
Filename: libraries/Email.php
Line Number: 937

This is due you need to define the config['charset'] in the email.php file in the config directory of the app.
$config['charset']          = null; //original
$config['charset']          = 'UTF-8';   //or whatever is good for your app.

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Este error de strpos(): Empty needle en la librería Email.php significa que no se ha definido una variable llamada charset en el email.php del directorio config de su app.