The consistency of BatchFixedLagSmoother (enforceConsistency_=true) may not be maintained as expected?

[NewThinker-Jeffrey]

gtsam/gtsam/nonlinear/BatchFixedLagSmoother.cpp

Lines 268 to 273 in 23f4282

	if (enforceConsistency_ && (linearValues_.size() > 0)) {
	theta_.update(linearValues_);
	for(const auto key: linearValues_.keys()) {
	delta_.at(key) = newDelta.at(key);
	}
	}

It seems that the above lines are trying maintaining the consistency (First Estimate Jacobian) of the smoother, but the linearValues_ are set nowhere, so actually the above lines won't be reached ever. Is this a bug or the consistency is handled elsewhere?