Correction in regex

The old version caused problems when the host is an IP address. The new version will not match with JPEG 2000 (.JP2) images though.

wp-tevko-responsive-images.php

@@ -334,7 +334,7 @@ function tevkori_filter_content_images_callback( $matches ) {
 	if ( false !== strpos( 'srcset="', $atts ) ) {
 
 		// Get the url of the original image.
-        preg_match( '/src="(.+?)(\-([0-9]+)x([0-9]+))?(\.\w{3,4})"/i', $atts, $url_matches );
+        preg_match( '/src="(.+?)(\-([0-9]+)x([0-9]+))?(\.[a-zA-Z]{3,4})"/i', $atts, $url_matches );
 
 		$url = $url_matches[1] . $url_matches[5];