Fixing Warning: session_start(): Cannot send session cache limiter – headers already sent (output started at /home/xxxxx/public_html/wp-content/plugins/pdf-viewer-for-wordpress/web/viewer-shortcode.php:3)

We received this issue from a few users. So, We did a workaround and made a way to fix. Some servers add spaces to uploaded files somehow, for encoding type I think but not totally sure. However, due to extra spaces, there's a warning message displays on top of Viewer. Warning: session_start(): Cannot send session [...]