Preserve backwards compatibility for view settings.

src/ui/MainWindow.h

@@ -304,7 +304,9 @@ protected:
         VIEW_MISSION,          // Mission/Map/Plan view mode. Used for setting mission waypoints and high-level system commands.
         VIEW_FLIGHT,           // Flight/Fly/Operate view mode. Used for 1st-person observation of the vehicle.
         VIEW_SIMULATION,       // HIL Simulation view. Useful overview of the entire system when doing hardware-in-the-loop simulations.
+        UNUSED1,               // Unused spacer for backwards compatibility with older settings files.
         VIEW_SETUP,            // Setup view. Used for initializing the system for operation. Includes UI for calibration, firmware updating/checking, and parameter modifcation.
+        UNUSED2,               // Unused spacer for backwards compatibility with older settings files.
         VIEW_TERMINAL,         // Terminal interface. Used for communicating with the remote system, usually in a special configuration input mode.
         VIEW_LOCAL3D,          // A local 3D view. Provides a local 3D view that makes visualizing 3D attitude/orientation/pose easy while in operation.
         VIEW_GOOGLEEARTH       // 3D Google Earth view. A 3D terrain view, though the vehicle is still 2D.