AP_InertialSensor: correct INS_generic example

segfaults due to lack of singletoin objects in examples

libraries/AP_InertialSensor/examples/INS_generic/INS_generic.cpp

@@ -7,6 +7,7 @@
 #include <AP_InertialSensor/AP_InertialSensor.h>
 #include <AP_ExternalAHRS/AP_ExternalAHRS.h>
 #include <AP_Logger/AP_Logger.h>
+#include <GCS_MAVLink/GCS_Dummy.h>
 
 const AP_HAL::HAL &hal = AP_HAL::get_HAL();
 
@@ -184,4 +185,9 @@ static void run_test()
     }
 }
 
+const struct AP_Param::GroupInfo        GCS_MAVLINK_Parameters::var_info[] = {
+    AP_GROUPEND
+};
+GCS_Dummy _gcs;
+
 AP_HAL_MAIN();