Fatal error: Call to undefined function M_get_charset_collate() in .../wp-content/plugins/membershi

For the testing my site, from the main site I registered as a new user at /wp-signup.php

That all went ok - registered a new username, password, then site name to create a new site as a subfolder (not subdomain). Activated the new site using the emailed activation link. Then when I try to login I get this.

Fatal error: Call to undefined function M_get_charset_collate() in /home/.../public_html/.../wp-content/plugins/membership/membershipincludes/addons/newsstream.php on line 27

Why does the logging in process need to reference the plugins/membership/ ?

In the root site I do not need or want to avtivate Membership as there is no content I need to protect.

I DO need Membership to be activated for my site admins (their sites in subdirectory), so *they* can protect their content for their users. Upgraded SitePro site admins then get access to Membership, while free basic users do not.

This test was to create a new user and site, without using SitePro to upgrade to pro (I am using SitePro on the root site to then upgrade site admins so their site gets additional features). So this test registration was the intial stage of a site admin signing up.

How can I make this site admin registration login not require/reference the Membership plugin ?

Given that I do not need/want Membership activated in the root www. site, how should this work?

Is there a setting I have missed?