sidebar modules tab activation button not present in CoC Ruleset

[similarly]

When I open the "modules" tab under library in the new sidebar, on the modules window, the "activation" button is present in my 5e campaign, but is not present in the Call of Cthulhu 7e campaign.
Also, when I go into options and module activation, and click on a module, I get an error message:
[ERROR] Script execution error: [string "library_booklistentry"]:3: attempt to index a nil value.

50413

[similarly]

Never mind! It was an extension: Unity Compatible Better Module Window. I disabled it. Will contact author. Everything's fine!