GCS_MAVLink: make guided-mode-change-alt and guided-mode-wp dependant on AP_MISSION_ENABLED

We really should not be using Mission_Command to transfer information between the base-class GCS_MAVLink and subclasses like GCS_MAVLink_Plane.  But until we fix that we can exclude the code if Mission is not available (like on peripherals...)

libraries/GCS_MAVLink/GCS_Common.cpp

@@ -54,6 +54,7 @@
 #include <AP_Scripting/AP_Scripting.h>
 #include <SRV_Channel/SRV_Channel.h>
 #include <AP_Winch/AP_Winch.h>
+#include <AP_Mission/AP_Mission.h>
 #include <AP_OpenDroneID/AP_OpenDroneID.h>
 #include <AP_OSD/AP_OSD.h>
 #include <AP_RCTelemetry/AP_CRSF_Telem.h>
@@ -887,19 +888,31 @@ void GCS_MAVLINK::handle_mission_item(const mavlink_message_t &msg)
     if (msg.msgid == MAVLINK_MSG_ID_MISSION_ITEM) {
         mavlink_mission_item_t mission_item;
         mavlink_msg_mission_item_decode(&msg, &mission_item);
+#if AP_MISSION_ENABLED
         MAV_MISSION_RESULT ret = AP_Mission::convert_MISSION_ITEM_to_MISSION_ITEM_INT(mission_item, mission_item_int);
         if (ret != MAV_MISSION_ACCEPTED) {
             const MAV_MISSION_TYPE type = (MAV_MISSION_TYPE)mission_item_int.mission_type;
             send_mission_ack(msg, type, ret);
             return;
         }
+#else
+        // No mission library, so we can't convert from MISSION_ITEM
+        // to MISSION_ITEM_INT.  Since we shouldn't be receiving fence
+        // or rally items via MISSION_ITEM, we don't need to work hard
+        // here, just fail:
+        const MAV_MISSION_TYPE type = (MAV_MISSION_TYPE)mission_item.mission_type;
+        send_mission_ack(msg, type, MAV_MISSION_UNSUPPORTED);
+        return;
+#endif
         send_mission_item_warning = true;
     } else {
         mavlink_msg_mission_item_int_decode(&msg, &mission_item_int);
     }
-    const uint8_t current = mission_item_int.current;
     const MAV_MISSION_TYPE type = (MAV_MISSION_TYPE)mission_item_int.mission_type;
 
+#if AP_MISSION_ENABLED
+    const uint8_t current = mission_item_int.current;
+
     if (type == MAV_MISSION_TYPE_MISSION && (current == 2 || current == 3)) {
         struct AP_Mission::Mission_Command cmd = {};
         MAV_MISSION_RESULT result = AP_Mission::mavlink_int_to_mission_cmd(mission_item_int, cmd);
@@ -925,6 +938,7 @@ void GCS_MAVLINK::handle_mission_item(const mavlink_message_t &msg)
         send_mission_ack(msg, MAV_MISSION_TYPE_MISSION, result);
         return;
     }
+#endif
 
     // not a guided-mode reqest
     MissionItemProtocol *prot = gcs().get_prot_for_mission_type(type);

libraries/GCS_MAVLink/GCS_config.h

@@ -89,7 +89,7 @@
 // sending warnings to the GCS in Sep 2022 if this command was used.
 // Copter 4.4.0 sends this warning.
 #ifndef AP_MAVLINK_MSG_MISSION_REQUEST_ENABLED
-#define AP_MAVLINK_MSG_MISSION_REQUEST_ENABLED 1
+#define AP_MAVLINK_MSG_MISSION_REQUEST_ENABLED AP_MISSION_ENABLED
 #endif
 
 // all commands can be executed by COMMAND_INT, so COMMAND_LONG isn't