Quick fix on line 31 to prevent error when using it with Joomla! Webservices Api

plg_content_responsive.php

<?php
/**
 * @package     ttc-freebies.plugin-responsive-images
 *
 * @copyright   Copyright (C) 2017 Dimitrios Grammatikogiannis. All rights reserved.
 * @license     GNU General Public License version 2 or later; see LICENSE.txt
 */
defined('_JEXEC') || die;

use Joomla\CMS\Plugin\CMSPlugin;

/**
 * Content responsive images plugin
 */
class PlgContentResponsive extends CMSPlugin
{
	/**
	 * System std Event Prepare
	 *
	 * @param string   $context  The context of the content being passed to the plugin.
	 * @param object   &$row     The article object.  Note $article->text is also available
	 * @param mixed    &$params  The article params
	 * @param integer  $page     The 'page' number
	 *
	 * @return  mixed  Always returns void or true
	 *
	 * @throws Exception
	 *
	 * @since   4.0.0
	 */
	public function onContentPrepare($context, &$row, &$params, $page = 0)
	{
		$this->mainLogic($context, $row, true);
	}
	
	/**
	 * System std Event After Save
	 *
	 * @param string   $context   The context of the content being passed to the plugin.
	 * @param object   &$article  The article object.  Note $article->text is also available
	 * @param mixed    &$params  The article params
	 * @param integer  $page     The 'page' number
	 *
	 * @return  mixed  Always returns void or true
	 *
	 * @throws Exception
	 *
	 * @since   4.0.0
	 */
	public function onContentAfterSave($context, &$article, &$params)
	{
		$this->mainLogic($context, $article, false);
	}
	
	/**
	 * Creates all the image sizes on the fly on the save and optionally changes markup
	 *
	 * @param string   $context   The context of the content being passed to the plugin.
	 * @param object   &$article  The article object.  Note $article->text is also available
	 * @param mixed    &$params  The article params
	 * @param integer  $page     The 'page' number
	 *
	 * @return  mixed  Always returns void or true
	 *
	 * @throws Exception
	 *
	 * @since   4.0.0
	 */
	private function mainLogic($context, &$row, $replaceTags = false)
	{
		// Bail out if the helper isn't loaded
		if (!class_exists('\Ttc\Freebies\Responsive\Helper')) {
			return;
		}
		
		$pluginComponents = $this->params->get('components');
		
		if (!is_object($pluginComponents)) {
			try {
				$pluginComponents = \json_decode($this->params->get('components'));
			} catch (\Exception $e) {
				return;
			}
			
			if ($pluginComponents === false) {
				return;
			}
		}
		
		if ((array) $pluginComponents) {
			foreach ($pluginComponents as $key => $component) {
				$views = preg_split('/[\s,]+/', $component->component_view);
				if ($views === '') {
					continue;
				}
				
				foreach ($views as $view) {
					if ($context !== $component->component_name . '.' . $view && substr($component->component_name, 0, 4) !== "mod_") {
						continue;
					}
					
					$columns = preg_split('/[\s,]+/', $component->component_db_column);
					if ($columns === '') {
						continue;
					}
					
					foreach ($columns as $currentNeedle) {
						// $currentNeedle = $component->component_db_columnn;
						$matches = [];
						if (!empty($row->{$currentNeedle})) {
							if (!preg_match_all('#<img\s[^>]+>#', $row->{$currentNeedle}, $matches)) {
								continue;
							}
							
							if (count($matches)) {
								foreach ($matches[0] as $img) {
									// Make sure we have a src
									if (strpos($img, ' src=') !== false && strpos($img, '//') === false) {
										$processed = (new \Ttc\Freebies\Responsive\Helper)->transformImage($img, [200, 320, 480, 768, 992, 1200, 1600, 1920]);
										if ($replaceTags && $processed !== $img) {
											$row->{$currentNeedle} = str_replace($img, $processed, $row->{$currentNeedle});
										}
									}
								}
							}
						}
					};
				};
				
				if (substr($component->component_name, 0, 4) === "mod_") {
					$columns = preg_split('/[\s,]+/', $component->component_db_column);
					if ($columns === '') {
						continue;
					}
					
					foreach ($columns as $currentNeedle) {
						// $currentNeedle = $component->component_db_columnn;
						$matches = [];
						if (!empty($row->{$currentNeedle})) {
							if (!preg_match_all('#<img\s[^>]+>#', $row->{$currentNeedle}, $matches)) {
								continue;
							}
							
							if (count($matches)) {
								foreach ($matches[0] as $img) {
									// Make sure we have a src
									if (strpos($img, ' src=') !== false && strpos($img, '//') === false) {
										$processed = (new \Ttc\Freebies\Responsive\Helper)->transformImage($img, [200, 320, 480, 768, 992, 1200, 1600, 1920]);
										if ($replaceTags && $processed !== $img) {
											$row->{$currentNeedle} = str_replace($img, $processed, $row->{$currentNeedle});
										}
									}
								}
							}
						}
					};
				}
			}
		}
		return true;
	}
}