Theme Preview – Warning: Cannot modify header information

I am receiving the following error message when previewing themes

Warning: Cannot modify header information – headers already sent by (output started at /home/example/public_html/wp-content/plugins/shareaholic/utilities.php:1020) in /home/example/public_html/wp-includes/option.php on line 750

Warning: Cannot modify header information – headers already sent by (output started at /home/example/public_html/wp-content/plugins/shareaholic/utilities.php:1020) in /home/example/public_html/wp-includes/option.php on line 751

I am running a multisite network using WP 4.0. I have disabled all plugins except Shareaholic to test the theme previewer. It still displays the error as the theme preview loads.

Any ideas on how to fix this?

https://ww.wp.xz.cn/plugins/shareaholic/