Installer uninstalls needed components

Steps to reproduce:
1. Open Qt Installer and log in
2. Open settings and unselect maintenancetool repository
3. Install some Qt version
4. Run maintenancetool
5. Open settings and unselect maintenancetool repository
6. Go to component selection page and select anything (do not touch items under 'Build tools')
7. Go to next page

Result:
Qt version which was selected in step 3 gets uninstalled

Expected:
Only newly selected items will be installed

Reason for excess uninstall is that Qt version is dependent on 'Build tools'. The 'Build tools' is not marked as partially checked as it contains only virtual components, causing the 'Build tools' to be uninstalled which pulls the components depending on it on uninstall as well.