ArduPlane: init DataFlash obj

ArduPlane/system.pde

@@ -133,6 +133,7 @@ static void init_ardupilot()
     mavlink_system.sysid = g.sysid_this_mav;
 
 #if LOGGING_ENABLED == ENABLED
+    DataFlash.Init();
     if (!DataFlash.CardInserted()) {
         gcs_send_text_P(SEVERITY_LOW, PSTR("No dataflash card inserted"));
         g.log_bitmask.set(0);