Add checking of Display on Screen Flag for single screen outputs.

Fixes: https://launchpad.net/bugs/730160

openlp/core/ui/maindisplay.py

@@ -425,6 +425,13 @@ class MainDisplay(DisplayWidget):
         if self.isLive:
             if self.hideMode:
                 self.hideDisplay(self.hideMode)
+            else:
+                # Single screen active
+                if self.screens.monitor_number == 0:
+                    # Only make visible if setting enabled
+                    if QtCore.QSettings().value(u'general/display on monitor',
+                        QtCore.QVariant(True)).toBool():
+                        self.setVisible(True)
                 else:
                     self.setVisible(True)
         preview = QtGui.QImage(self.screen[u'size'].width(),