KMix: fixed runtime crash happening when only one mixer is available and the user chooses 'Show Master Channel...' from RMB menu.

Signed-off-by: Michele Calgaro <michele.calgaro@yahoo.it>

kmix/dialogselectmaster.cpp

@@ -114,12 +114,15 @@ void DialogSelectMaster::show(Mixer *curr_mixer)
     }
     masterSelectionChanged(0);
 
-    for (Mixer *mixer = Mixer::mixers().first(); mixer; mixer = Mixer::mixers().next())
+    if (Mixer::mixers().count() > 1)
     {
-	if (curr_mixer == mixer)
-	{
-	    m_cMixer->setCurrentItem(mixer->mixerName());
-	}
+        for (Mixer *mixer = Mixer::mixers().first(); mixer; mixer = Mixer::mixers().next())
+        {
+	    if (curr_mixer == mixer)
+	    {
+                m_cMixer->setCurrentItem(mixer->mixerName());
+	    }
+        }
     }
     createPage(curr_mixer);