Rover: balance bot stands in acro with no position estimate

Rover/mode_acro.cpp

@@ -9,6 +9,12 @@ void ModeAcro::update()
         float desired_throttle;
         // convert pilot stick input into desired steering and throttle
         get_pilot_desired_steering_and_throttle(desired_steering, desired_throttle);
+
+        // if vehicle is balance bot, calculate actual throttle required for balancing
+        if (rover.is_balancebot()) {
+            rover.balancebot_pitch_control(desired_throttle);
+        }
+
         // no valid speed, just use the provided throttle
         g2.motors.set_throttle(desired_throttle);
     } else {