Small mistake in class-coblocks-generated-styles.php

Hi. In some situations styles() in class-coblocks-generated-styles.php can return null, which will then be passed to wp_add_inline_style(). This is not good, because then null gets into the stripos() and it gives “deprecated” message in PHP 8.1:

PHP Deprecated:  stripos(): Passing null to parameter #1 ($haystack) of type string is deprecated in \wp-includes\functions.wp-styles.php on line 90

To avoid this, you need to add a check in plugin function. Here is the fix:

/**
 * Footer Styling
 *
 * @access public
 */
public function enqueue_styles() {
	$style = $this->styles();
	if (!is_null($style)) {
		wp_add_inline_style( 'coblocks-frontend', $style );
	}
}