Add author to display posts shortcode

gistfile1.php

<?php
/**
 * Add Author to Display Posts Shortcode plugin
 * @author Bill Erickson
 * @link http://wordpress.org/extend/plugins/display-posts-shortcode/
 *
 * @param $output string, the original markup for an individual post
 * @param $atts array, all the attributes passed to the shortcode
 * @param $image string, the image part of the output
 * @param $title string, the title part of the output
 * @param $date string, the date part of the output
 * @param $excerpt string, the excerpt part of the output
 * @param $inner_wrapper string, what html element to wrap each post in (default is li)
 * @return $output string, the modified markup for an individual post
 */
 
add_filter( 'display_posts_shortcode_output', 'be_display_posts_facebook', 10, 7 );
function be_display_posts_facebook( $output, $atts, $image, $title, $date, $excerpt, $inner_wrapper ) {
	
	// Here's the author
	$author = '<span class="author">by ' . get_the_author() . '</span>';
	
	// Now let's rebuild the output and add the $author to it
	$output = '<' . $inner_wrapper . ' class="listing-item">' . $image . $title . $date . $author . $excerpt . '</' . $inner_wrapper . '>';
	
	// Finally we'll return the modified output
	return $output;
}

This is my first Gihub comment so apologies for any noobness.

Is there not an error on line 21 whereby there should NOT be a quote before "by" and there SHOULD be a quote after ""