Tab hiding is inconsistent

[AlUlkesh]

There are currently two methods to hide an image browser tab:

• List of active tabs in Settings
• Enable Maintenance tab

All tabs should be able to be set via List of active tabs.

The problem here is, that image browser needs to be able to differentiate between "not in List of active tabs, because User removed it" and "not in List of active tabs, because it is a new default tab".

[AlUlkesh]

This should fix that. If you had disabled the Maintenance tab before, you'll have to remove it from the List of active tabs again.