RemoveConstraint error

[Seahorse]

Code:

        public void RemoveConstraint(int constraintIndex)
        {
            SwapConstraints(constraintIndex, constraintCount - 1);
            m_IDs.RemoveAt(constraintCount - 1);
            m_IDToIndex.RemoveAt(constraintCount - 1);

            m_ConstraintCount--;
            m_ActiveConstraintCount = Mathf.Min(m_ActiveConstraintCount, m_ConstraintCount);
        }

One mystery: Why is the count of m_IDs and m_IDToIndex is 0? solver batch