If we fail to connect to pulse, don't enumerate sinks or sources.

Otherwise the pulse client library dislikes having methods called
with a null context.

Change-Id: I96629065b7a0e36e0d10402526cb167e65458e27
Reviewed-by: Jonas Rabbe <jonas.rabbe@nokia.com>

src/plugins/pulseaudio/qpulseaudioengine.cpp

@@ -264,10 +264,12 @@ QPulseAudioEngine::QPulseAudioEngine(QObject *parent)
 
     pa_threaded_mainloop_unlock(m_mainLoop);
 
+    if (ok) {
         serverInfo();
         sinks();
         sources();
     }
+}
 
 QPulseAudioEngine::~QPulseAudioEngine()
 {