Check for OA interface failures only after it has been activated

The OA interface is 'activated' when it receives the first trajectory message.

src/lib/avoidance/ObstacleAvoidance.cpp

@@ -86,8 +86,12 @@ void ObstacleAvoidance::injectAvoidanceSetpoints(Vector3f &pos_sp, Vector3f &vel
 	}
 
 	if (avoidance_invalid) {
+		if (_avoidance_activated) {
+			// Invalid point received: deactivate
 			PX4_WARN("Obstacle Avoidance system failed, loitering");
 			_publishVehicleCmdDoLoiter();
+			_avoidance_activated = false;
+		}
 
 		if (!_failsafe_position.isAllFinite()) {
 			// save vehicle position when entering failsafe
@@ -98,10 +102,15 @@ void ObstacleAvoidance::injectAvoidanceSetpoints(Vector3f &pos_sp, Vector3f &vel
 		vel_sp.setNaN();
 		yaw_sp = NAN;
 		yaw_speed_sp = NAN;
+
+		// Do nothing further - wait until activation
 		return;
 
-	} else {
+	} else if (!_avoidance_activated) {
+		// First setpoint has been received: activate
+		PX4_INFO("Obstacle Avoidance system activated");
 		_failsafe_position.setNaN();
+		_avoidance_activated = true;
 	}
 
 	if (avoidance_point_valid && !wp_msg_timeout) {

src/lib/avoidance/ObstacleAvoidance.hpp

@@ -130,6 +130,8 @@ protected:
 	matrix::Vector3f _position = {}; /**< current vehicle position */
 	matrix::Vector3f _failsafe_position = {}; /**< vehicle position when entered in failsafe */
 
+	bool _avoidance_activated{false}; /**< true after the first avoidance setpoint is received */
+
 	systemlib::Hysteresis _avoidance_point_not_valid_hysteresis{false}; /**< becomes true if the companion doesn't start sending valid setpoints */
 	systemlib::Hysteresis _no_progress_z_hysteresis{false}; /**< becomes true if the vehicle is not making progress towards the z component of the goal */