Qt4Target setup page: Do not enable targets without buildconfigurations

Typo in the code found by clang

Change-Id: Ibe1b7711625049418792013609467d4d34e0f886
Reviewed-on: http://codereview.qt.nokia.com/364


Reviewed-by: Qt Sanity Bot <qt_sanity_bot@ovi.com>
Reviewed-by: Tobias Hunger <tobias.hunger@nokia.com>