Guarding existing variables which were introduced in 1.7.3, but never implemented in the configurator until now.

Note that these are for the moment just passive passengers -- there's no UI in the configurator to edit them yet.

js/msp/MSPHelper.js

@@ -1208,6 +1208,7 @@ var mspHelper = (function (gui) {
                 buffer.push(lowByte(FAILSAFE_CONFIG.failsafe_throttle_low_delay));
                 buffer.push(highByte(FAILSAFE_CONFIG.failsafe_throttle_low_delay));
                 buffer.push(FAILSAFE_CONFIG.failsafe_procedure);
+                if (semver.gte(CONFIG.flightControllerVersion, "1.7.3")) {
                     buffer.push(FAILSAFE_CONFIG.failsafe_recovery_delay);
                     buffer.push(lowByte(FAILSAFE_CONFIG.failsafe_fw_roll_angle));
                     buffer.push(highByte(FAILSAFE_CONFIG.failsafe_fw_roll_angle));
@@ -1217,6 +1218,7 @@ var mspHelper = (function (gui) {
                     buffer.push(highByte(FAILSAFE_CONFIG.failsafe_fw_yaw_rate));
                     buffer.push(lowByte(FAILSAFE_CONFIG.failsafe_stick_motion_threshold));
                     buffer.push(highByte(FAILSAFE_CONFIG.failsafe_stick_motion_threshold));
+                }   
                 if (semver.gte(CONFIG.flightControllerVersion, "1.7.4")) {
                     buffer.push(lowByte(FAILSAFE_CONFIG.failsafe_min_distance));
                     buffer.push(highByte(FAILSAFE_CONFIG.failsafe_min_distance));