QMake: Do not warn when using default mkspec

Change-Id: I945d3fa33193394e00842cf4f6d2f1bb2852033d
Reviewed-by: Tobias Hunger <tobias.hunger@nokia.com>

src/plugins/qt4projectmanager/qmakestep.cpp

@@ -698,7 +698,7 @@ void QMakeStepConfigWidget::updateSummaryLabel()
     if (!tc)
         return;
     QList<Utils::FileName> tcSpecList = tc->mkspecList();
-    if (!tcSpecList.contains(m_step->mkspec()))
+    if (!tcSpecList.isEmpty() && !tcSpecList.contains(m_step->mkspec()))
         setAdditionalSummaryText(tr("<b>Warning:</b> The tool chain suggests using another mkspec."));
     else
         setAdditionalSummaryText(QString());