Fix edge case in hasDeltaYaw logic

- Fixes edge case where if deltaYaw WAS valid, went NAN and then became
  valid again (by sending exactly 0.0), we would not consider it valid.

Author: jnomikos

src/Gimbal/Gimbal.h

@@ -51,7 +51,7 @@ class Gimbal : public FactGroup
     void setAbsolutePitch(float absPitch) { absolutePitch()->setRawValue(absPitch); }
     void setBodyYaw(float yaw) { bodyYaw()->setRawValue(yaw); }
     void setAbsoluteYaw(float absYaw) { absoluteYaw()->setRawValue(absYaw); }
-    void setDeltaYaw(float delta) { deltaYaw()->setRawValue(delta); }
+    void setDeltaYaw(float delta) { deltaYaw()->setRawValue(delta); _receivedDeltaYaw = true; }
     void setDeviceId(uint id) { deviceId()->setRawValue(id); }
     void setManagerCompid(uint id) { managerCompid()->setRawValue(id); }
 
@@ -65,7 +65,7 @@ class Gimbal : public FactGroup
     void setCapabilityFlags(uint32_t flags);
     bool supportsRetract() const { return (_capabilityFlags & GIMBAL_MANAGER_CAP_FLAGS_HAS_RETRACT) != 0; }
     bool supportsYawLock() const { return (_capabilityFlags & GIMBAL_MANAGER_CAP_FLAGS_HAS_YAW_LOCK) != 0; }
-    bool hasDeltaYaw() { return !qIsNaN(deltaYaw()->rawValue().toFloat()); }
+    bool hasDeltaYaw() { return _receivedDeltaYaw; }
 
 signals:
     void pitchRateChanged();
@@ -85,6 +85,7 @@ class Gimbal : public FactGroup
     bool _receivedGimbalManagerInformation = false;
     bool _receivedGimbalManagerStatus = false;
     bool _receivedGimbalDeviceAttitudeStatus = false;
+    bool _receivedDeltaYaw = false;
     bool _isComplete = false;
     bool _neutral = false;
     uint32_t _capabilityFlags = 0; // GIMBAL_MANAGER_CAP_FLAGS

src/Gimbal/GimbalController.cc

@@ -242,7 +242,7 @@ void GimbalController::_handleGimbalDeviceAttitudeStatus(const mavlink_message_t
 
     const float deltaYawDeg = qRadiansToDegrees(attitude_status.delta_yaw);
     // Extension field: unsent decodes as 0.0, so ignore 0 until a value proves support.
-    if (!qIsNaN(gimbal->deltaYaw()->rawValue().toFloat()) || attitude_status.delta_yaw != 0.0f) {
+    if (gimbal->hasDeltaYaw() || attitude_status.delta_yaw != 0.0f) {
         gimbal->setDeltaYaw(deltaYawDeg);
     }