[DO NOT MERGE] Fix vue router paths

[fschade]

fixes owncloud/ocis#988

[update-docs]

Thanks for opening this pull request! The maintainers of this repository would appreciate it if you would create a changelog item based on your changes.

[kulmann]

Navigating into random folders, I see two issues:
1: [vue-router] missing param for named route "files-list": Expected "item" to be defined
2: empty folders list their own folder name as subfolder, although it doesn't exist (create a folder test, navigate into it. You will see a folder test in the list although you just created the parent and it is empty).

[butonic]

outdated. will be fixed by moving to the new vue router. tracked in #5269