Comparing a std::string to an empty string literal is more complex than using the std::string::empty() function. Improve the code efficiency by replacing the former with the latter. Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> Reviewed-by: Paul Elder <paul.elder@ideasonboard.com> Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>