"Generate seed" doesn't work if user already has buckets in their account

[MeijeSibbel]

We are missing the case where the user already has buckets in their account and presses "Generate seed" in the app. Currently this doesn't work and they have to manually create a bucket called Goobox first. This is impractical as very confusing for the user because they automatically click on "generate seed" if they don't know which seed to enter.

We should make it so that "Generate seed" generates a seed for the goobox folder, even if they already have buckets in their account.