Fix QML corner cases, simplify instructions, add need to manually re-connect

src/AutoPilotPlugins/PX4/AirframeComponent.qml

@@ -111,7 +111,7 @@ QGCView {
         QGCLabel {
             anchors.top:    headingSpacer.bottom
             width:          parent.width - applyButton.width - 5
-            text:           "Select your airframe type and specific vehicle bellow. Click 'Apply and Restart' when ready and your vehicle will be disconnected, rebooted to the new settings and re-connected."
+            text:           "Please select your airframe type. Click 'Apply and Restart' to reboot the autopilot. Please re-connect then manually."
             wrapMode:       Text.WordWrap
         }
 
@@ -221,11 +221,14 @@ QGCView {
                             anchors.top: image.bottom
                             width:  parent.width - (innerMargin * 2)
                             model:  modelData.airframes
-                            currentIndex: (modelData.name == controller.currentAirframeType) ? controller.currentVehicleIndex : 0
+                            currentIndex: (modelData.name == controller.currentAirframeType) ? controller.currentVehicleIndex : -1
 
                             onActivated: {
-                                controller.autostartId = modelData.airframes[currentIndex].autostartId
-                                airframeCheckBox.checked = true;
+                                if (index != -1) {
+                                    currentIndex = index
+                                    controller.autostartId = modelData.airframes[index].autostartId
+                                    airframeCheckBox.checked = true;
+                                }
                             }
                         }
                     }