HHVM + SmartCrawl throws PHP Warning

Hey guys,

Would like yo know if you guys could look into a strange occurrence again. When I enabled HHVM on the server level SmartCrawl now throws the following PHP warning:

trim() expects parameter 1 to be string, array given

For:

wp-content/plugins/wpmu-dev-seo/includes/tools/onpage.php:73

With the call stack:

trim()
wp-content/plugins/wpmu-dev-seo/includes/tools/onpage.php:73

WDS_OnPage->wds_stop_title_buffer()
wp-content/plugins/wpmu-dev-seo/includes/tools/onpage.php:196

WDS_OnPage->wds_head()
wp-includes/class-wp-hook.php:298

do_action('wp_head')
wp-includes/general-template.php:2589

wp_head()
wp-content/themes/***/header.php:24

load_template('~/wp-content/themes/***/header.php')
wp-includes/template.php:647

locate_template()
wp-includes/general-template.php:45

get_header()
wp-content/themes/***/page.php:18

Please advise. Thanks again.