Fix: if bootstrap failed, it could end with an empty screen instead of error

There are various of ways bootstrap can fail:
- Failing network connection
- Incomplete download
- No write permissions
- Disk full
- (others I forgot)

They all result in a screen with no windows. To ensure we at least
always show something when anything bad happens, if the bootstrap
is not successful, show a screen what the next step for the human
should be.