Effects are sometimes visible in Content Library without adding QtQuick3D module first

Steps to reproduce:

• Start Design Studio
• Open some previous 3D project (that has QtQuick3D module imported)
• Close the project, but do not close DS
• Create new general empty project
• -> Effects are visible in Content Library / Effects, even though QtQuick3D module is not added yet. Expected is to show message "To use Content Library, first add the QtQuick3D module in the Components view."