Linear initial equations with non-fixed parameters are detected as nonlinear

[Patrick Täuber]

In the following model the linear initial equation system is considered as nonlinear due to the wrong Jacobian type:

model foo
  final parameter Real p1 = 1;
  final parameter Real p2 = 2;
  final parameter Real p3 = 3;
  final parameter Real p4 = 4;
  parameter Real q1 (fixed=false);
  parameter Real q2 (fixed=false);
initial equation
  -p1 = 3 * (p3 * q1 + p4 * q2);
  -p2 = 3 * (q1 * p4 - p3 * q2);
end foo;