WordPress 4.5 - built in theme logo support

Hi, I used this code to try to set a DEFAULT logo in my theme but it’s not working.
Is there a problem with the syntax maybe - mix of " and ’ in the code.
Any ideas?
Thanks!

add_filter('get_custom_logo',function($html){
   if(empty($html)) { 
	 $html = '<img src = get_template_uri() . "/img/logo.jpg" >'; 
   } 
   return $html;
});