Added a root loader to help deep nested children to show an element in the...

Added a root loader to help deep nested children to show an element in the middle of the root Window.

src/FlightDisplay/FlightDisplayView.qml

@@ -264,7 +264,7 @@ QGCView {
                 anchors.top:        parent.top
                 anchors.bottom:     parent.bottom
                 width:              height
-                radius:             QGroundControl.videoManager.videoReceiver && QGroundControl.videoManager.videoReceiver.recording ? 0 : height
+                radius:             QGroundControl.videoManager && QGroundControl.videoManager.videoReceiver && QGroundControl.videoManager.videoReceiver.recording ? 0 : height
                 color:              "red"
             }
 

src/ui/MainWindowInner.qml

@@ -530,5 +530,14 @@ Item {
             }
         }
     }
+
+    //-------------------------------------------------------------------------
+    //-- Loader helper for any child, no matter how deep can display an element
+    //   in the middle of the main window.
+    Loader {
+        id: rootLoader
+        anchors.centerIn: parent
+    }
+
 }