Don't call session manager function if not enabled

If session management has been disabled we will get a compilation
failure if we try to call QApplication::commitData() so don't do so if
it is disabled.

Upstream-Status: Pending

Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>

--- a/src/app/qmmpapplication.cpp
+++ b/src/app/qmmpapplication.cpp
@@ -29,6 +29,8 @@ void QmmpApplication::commitData(QSessionManager &manager)
 {
     if(UiHelper::instance())
         UiHelper::instance()->exit();
+#ifndef QT_NO_SESSIONMANAGER
     else
         QApplication::commitData(manager);
+#endif
 }