Fix QtVersion::invalidReason for symbian/desktop/simulator

Actually pass on the base qt version value...
Also fix a small issue on the qt versions page that prevented the
invalid reason showing up for a nameless version

Task-Nr: QTCREATORBUG-4899

src/plugins/qt4projectmanager/qt-desktop/desktopqtversion.cpp

@@ -84,7 +84,7 @@ QString DesktopQtVersion::invalidReason() const
     QString tmp = BaseQtVersion::invalidReason();
     if (tmp.isEmpty() && qtAbis().isEmpty())
         return QCoreApplication::translate("QtVersion", "Failed to detect the ABI(s) used by the Qt version.");
-    return QString();
+    return tmp;
 }
 
 QList<ProjectExplorer::Abi> DesktopQtVersion::qtAbis() const

src/plugins/qt4projectmanager/qt-desktop/simulatorqtversion.cpp

@@ -84,7 +84,7 @@ QString SimulatorQtVersion::invalidReason() const
     QString tmp = BaseQtVersion::invalidReason();
     if (tmp.isEmpty() && qtAbis().isEmpty())
         return QCoreApplication::translate("QtVersion", "Failed to detect the ABI(s) used by the Qt version.");
-    return QString();
+    return tmp;
 }
 
 QList<ProjectExplorer::Abi> SimulatorQtVersion::qtAbis() const

src/plugins/qt4projectmanager/qt-s60/symbianqtversion.cpp

@@ -107,7 +107,7 @@ QString SymbianQtVersion::invalidReason() const
             && (m_sbsV2Directory.isEmpty() || !QFileInfo(m_sbsV2Directory + QLatin1String("/sbs")).exists()))
         return QCoreApplication::translate("QtVersion", "SBS was not found.");
 
-    return QString();
+    return tmp;
 }
 
 bool SymbianQtVersion::toolChainAvailable(const QString &id) const

src/plugins/qt4projectmanager/qtoptionspage.cpp

@@ -757,6 +757,7 @@ void QtOptionsPageWidget::updateCurrentQtName()
         return;
     m_versions[currentItemIndex]->setDisplayName(m_versionUi->nameEdit->text());
     currentItem->setText(0, m_versions[currentItemIndex]->displayName());
+    updateDescriptionLabel();
 }