div property Null safety

Implementation

static final NormalOperation div = NormalOperation.floatOnly(
    floatCalc: (Model m) {
      final matX = m.x.asMatrix;
      if (matX != null && m.y.asMatrix == null) {
        // Page 179:  x is matrix, y is scalar
        final result = (m as Model15).matrices[m.resultMatrix];
        result.copyFrom(m, m.matrices[matX]);
        linalg.invert(result);
        final y = m.yF;
        result.visit((final int r, c) {
          result.setF(r, c, result.getF(r, c) * y);
        });
      } else {
        _scalarOrMatrix(m, scalar: (x, y) {
          if (x == 0) {
            throw CalculatorError(0);
          }
          return y / x;
        }, matrix: (m, x, y, r) {
          if (x != r) {
            r.resize(m, y.rows, y.columns);
          }
          try {
            linalg.solve(x, y, r);
          } on linalg.MatrixOverflow {
            m.floatOverflow = true;
          }
        });
      }
      m.needsSave = true;
    },
    complexCalc: (Model m) {
      if (m.x.asMatrix != null || m.y.asMatrix != null) {
        div.floatCalc!(m);
      } else if (m.xC == Complex.zero) {
        throw CalculatorError(0);
      } else {
        m.popSetResultXC = m.yC / m.xC;
      }
    },
    name: '/');