How to forbid installation of shared data if no optional sections was selected?

[WhiteOwl]

I have two applications which should be distributed together, but end-user can wish only one of them (or both at the same time). Both applications use the same set of additional files and registry keys (shared data).

So I did something like that:

code:
page components

Section "- shared"

  SetOutPath $instdir\data

SectionEnd

Section "Client A"

  SetOutPath $instdir\ClientA

SectionEnd

Section "Client B"

  SetOutPath $instdir\ClientB

SectionEnd

Data from section "- shared" should be installed for both clients, but if user uncheck both clients on components page, NSIS still will install "- shared" section.
How to forbid it? Or how to force user to check at least one of the clients?