Stop the media / presentation if going from Preview to Live

Fixes: https://launchpad.net/bugs/780095

openlp/core/ui/slidecontroller.py

@@ -1050,6 +1050,14 @@ class SlideController(QtGui.QWidget):
         """
         if QtCore.QSettings().value(u'advanced/double click live',
             QtCore.QVariant(False)).toBool():
+                # Live and Preview have issues if we have video or presentations
+                # playing in both at the same time.
+                if self.serviceItem.is_command():
+                    Receiver.send_message(u'%s_stop' %
+                        self.serviceItem.name.lower(),
+                        [self.serviceItem, self.isLive])
+                if self.serviceItem.is_media():
+                    self.onMediaClose()
                 self.onGoLive()
 
     def onGoLive(self):