PHP error in users.php line 721

I got this error while working on a totally different section of my website, it wasn’t even WordPress i was working on. When i was finished this error showed up
Warning: Invalid argument supplied for foreach() in /home/vhosts/www.mywebsite.org/wp-includes/user.php on line 721

I checked out the line where the error is and i can’t find anything wrong with it.

<strong>Line 721:</strong> foreach ( $metavalues as $meta ) {
		$value = maybe_unserialize($meta->meta_value);
		// Keys used as object vars cannot have dashes.
		$key = str_replace('-', '', $meta->meta_key);
		$user->{$key} = $value;
	}

Is there something wrong with it? I don’t know what $meta means it doesn’t say in users.php