Warning: count(): Parameter must be an array or an object that implements Countable in context_admin_context_admin_content_type_render()

With PHP 7.2 there is a warning: Warning: count(): Parameter must be an array or an object that implements Countable in context_admin_context_admin_content_type_render() (line 64 of context_admin/plugins/content_types/context_admin.inc).

This can be fixed by simplifying the logic with empty() there.