Nextcloud, error after restarting device

I have nextcloud installed, and not owncloud. I had a nextcloud file linked. Some time later, I opened the app and saw the following text in homepage:

```
Error
code: error
message: Attempt to invoke virtual method 'android.accountsAccount
com.owncloud.android.datamodel.FileDataStorageManager.getAccount()'
on a null object reference
```

I would be mostly fine with this, but if I try to link another file, the homepage does not change. Interestingly, the autocompletion does seem to see the newly linked file. Saving the transaction still leaves homepage showing error.

I'm able to reproduce this problem by linking a nextcloud file, restarting the device, and opening cone again. The same steps with Google Drive do not cause such an error.

v0.2.6+14

Reproduce the issue by linking a Nextcloud file, restarting the Android device, and reopening Cone; compare the behavior with Google Drive. Trace the linked-file and homepage update flow, using the reported null getAccount error as the starting point. Done means the homepage recovers after restart and reflects newly linked files.

Written by the indexing model from the issue text.