ekf2: add missing mag fuse type in enum

src/modules/ekf2/EKF/common.h

@@ -88,8 +88,9 @@ enum MagFuseType : uint8_t {
 	AUTO    = 0,   	///< The selection of either heading or 3D magnetometer fusion will be automatic
 	HEADING = 1,   	///< Simple yaw angle fusion will always be used. This is less accurate, but less affected by earth field distortions. It should not be used for pitch angles outside the range from -60 to +60 deg
 	MAG_3D  = 2,   	///< Magnetometer 3-axis fusion will always be used. This is more accurate, but more affected by localised earth field distortions
-	INDOOR  = 3,   	///< The same as option 0, but magnetometer or yaw fusion will not be used unless earth frame external aiding (GPS or External Vision) is being used. This prevents inconsistent magnetic fields associated with indoor operation degrading state estimates.
-	NONE    = 4    	///< Do not use magnetometer under any circumstance. Other sources of yaw may be used if selected via the EKF2_AID_MASK parameter.
+	UNUSED  = 3,    ///< Not implemented
+	INDOOR  = 4,   	///< The same as option 0, but magnetometer or yaw fusion will not be used unless earth frame external aiding (GPS or External Vision) is being used. This prevents inconsistent magnetic fields associated with indoor operation degrading state estimates.
+	NONE    = 5    	///< Do not use magnetometer under any circumstance. Other sources of yaw may be used if selected via the EKF2_AID_MASK parameter.
 };
 
 enum TerrainFusionMask : uint8_t {