breaks WordPress Appearance Customisation on 4.0

when this plugin is activated all of the admin pages for editing appearance (Themes, Customise, Widgets etc) generate a server error 500. As soon as plugin is deactivated functionality returns.

As a workaround I could deactivate the plugin every time I needed to change Appearance.

https://ww.wp.xz.cn/plugins/post-content-shortcodes/