Hi Eduardo,
No worries. These are PHP warnings, not errors. Unlike errors, warnings won’t break your website. They’re just messages aimed at developers to improve their code.
To hide this message, I suggest that you activate error logging on your website. Please keep WP_DEBUG to true and just paste the following code lines in your wp-config.php file, just before the line that says ‘That’s all, stop editing! Happy blogging.’:
// Enable WP_DEBUG mode
define( 'WP_DEBUG', true );
// Enable Debug logging to the /wp-content/debug.log file
define( 'WP_DEBUG_LOG', true );
// Disable display of errors and warnings
define( 'WP_DEBUG_DISPLAY', false );
@ini_set( 'display_errors', 0 );
More on this in the following topic: Debugging in WordPress
You will still be able to consult the warnings and errors triggered by your website but these won’t appear on your pages anymore.
Regards,