Fix disappearing configuration when disabling / re-enabling features

In Studio (sample project / branch in comments below)

Using TP 9.10

• Configure some users and groups (or any other feature that accepts a single instance)
• Save
• Disable feature
  => Configuration disappears

• - - -

Re enable existing users and groups in a existing project
=> configuration disappears

• - - -

Start a new configuration and disable it before saving
=> configuration disappears
This one may only be reproducible in FF