Fix message creation order

src/Vehicle/Vehicle.cc

@@ -263,11 +263,12 @@ void Vehicle::_sendMessage(mavlink_message_t message)
             // Give the plugin a chance to adjust
             _firmwarePlugin->adjustMavlinkMessage(&message);
             
+            static uint8_t messageKeys[256] = MAVLINK_MESSAGE_CRCS;
+            mavlink_finalize_message_chan(&message, mavlink->getSystemId(), mavlink->getComponentId(), link->getMavlinkChannel(), message.len, messageKeys[message.msgid]);
+            
             // Write message into buffer, prepending start sign
             uint8_t buffer[MAVLINK_MAX_PACKET_LEN];
             int len = mavlink_msg_to_send_buffer(buffer, &message);
-            static uint8_t messageKeys[256] = MAVLINK_MESSAGE_CRCS;
-            mavlink_finalize_message_chan(&message, mavlink->getSystemId(), mavlink->getComponentId(), link->getMavlinkChannel(), message.len, messageKeys[message.msgid]);
             
             link->writeBytes((const char*)buffer, len);
         }